# Depth of field: Full-frame lens vs. APS-C lens, both on APS-C sensor



## elemental (Oct 13, 2014)

Here's an odd question I've been struggling to work out in my head - if I'm missing an obvious answer, please feel free to point me to it - using Nikon terminology because it's easier (for me, at least):

Given the same focal length and aperture and the same sensor, will a larger-format lens produce a shallower depth of field than a smaller-format lens? For example, would a 35mm DX Nikon lens at f/4 on a DX-format camera produce the same depth field characteristics as a 35mm FX lens at f/4 on the same camera body? My brain says it has to, but when I sketch out the way I _think _it should work, my sketch says the larger-format lens is shallower. And let's say I'm just asking about the depth of field here, I know the actual appearance of out-of-focus areas is a much subtler phenomenon.

Also, good to see this place is still here! It's been a while.


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## Derrel (Oct 14, 2014)

IDENTICAL depth of field regardless if the lens is a DX-Nikkor, or a regular Nikkor. Just as a point of fact there have been a few lenses labeled as DX Nikkors, but there has never been any lens labeled as an "FX" lens. Not that you implied there had been, just wanted to point out that 99.9% of all lenses Nikon has made since 1959 have been Nikkors in F-mount.

Anyway, say you have the 35mm f/1.8 DX-Nikkor AKA "the cheap $199 one", and the newest 35mm Nikkor, the new 35mm f/1.8 G, AKA the "expensive one". EACH lens will give the same, exact depth of field at each and every f/stop when used on any DX-format Nikon camera body.

Same with the 55-200mm DX-Nikkor lenses, and corresponding focal lengths found on regular Nikkor zooms: at 85mm and f/8, the DOF will be the same on a 55-200 DX lens as it will be at f/8 on the 70-200 VR-II.

Also, since we're on the subject, a 35mm DX Nikkor has a focal length of 35 millimeters; the new 35/1.8 G-series Nikkor also has a 35 millimeter focal length, as does the older 35mm f/2 AF-D model. And the same is true of the 35mm f/1.4 AF-S G lens--it too is a 35 millimeter focal length lens. Your brain telling you that a DX lens and an FX lens of the same focal length on the same camera body will produce different depth of field characteristics is imaginary, and incorrect.


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## elemental (Oct 14, 2014)

Thanks Derrel – I knew in my head this had to be true, and I think I figured out the mistake in how I was sketching it.

Nikon 35mm F-mount lenses on DX was the simplest example I could think of to illustrate the question, but I'm actually thinking about 35mm SLR lenses on Micro Four-Thirds. Manual-focus lenses with focus peaking on a compact body seems like a great setup for travel, at least for me, and some of the mirrorless bodies remind me of the size of my KR-5 Super II, which I think is just about perfect for carrying around.


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## Braineack (Oct 14, 2014)

So you actually want to know if f/4 @ 35mm on a APC-S is the same as f/4 @ 35mm on a 4/3?

then, no.  No, it's not.

The 4/3 will have more DOF than the APC-S, and more than that of the FX, all other things being equal (including framing--which means distance to the subject is not the same).

example:

With a FX using a 55mm @ f1/6 with the distance to subject at 10ft, the total DOF is around 12ft.
With a DX (1.5x) using a 55mm @ f1/6 with the distance to subject at 15ft, the total DOF is around 18.5ft.
With a 4/3 (2.0x) using a 55mm @ f1/6 with the distance to subject at 20ft, the total DOF is around 25ft.


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## Ido (Oct 14, 2014)

Then on Micro Four Thirds, an adapted 35mm lens at f/4 and a native 35mm lens at f/4, from the same spot, focusing to the same distance, will give the same depth of field.


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## snowbear (Oct 14, 2014)

Correct.  DoF is determined by sensor or film size, aperture, distance to the subject and magnification.  All things being equal, the DoF will be the same.


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## KmH (Oct 14, 2014)

If the lens magnifies more or less but the sensor size and lens aperture does not change, _the point of focus distance has to change to keep subject scale constant if you want the DoF to stay constant._

So if one shot is made using a 50 mm lens, as sensor size and f-stop stay the same, and a second shot is made using a 200 mm lens the focus distance has to increase 4x to have the same DoF with the 200 mm lens the 50 mm lens had.


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## Braineack (Oct 14, 2014)

Ido said:


> Then on Micro Four Thirds, an adapted 35mm lens at f/4 and a native 35mm lens at f/4, from the same spot, focusing to the same distance, will give the same depth of field.



35mm is 35mm regardless of sensor size. (It's technically the distance of the glass from sensor plane when focused at infinity.)
f/4 is a function of diameter size to focal length.

So yes, the DOF will always be the same between two different 35mm lenses on a 4/3.


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## ruifo (Oct 14, 2014)

Read this article. It will help you on this:
What is equivalence and why should I care?: Digital Photography Review


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## elemental (Oct 15, 2014)

Thanks for all the replies. I'm quite comfortable with differences in depth of field and effective/equivalent focal length across format (I've been shooting 35mm and APS-C side-by-side for as long as I've had serious cameras), for some reason I got tripped up by the idea of a different size projected image (which, as we've established, isn't relevant).

I actually chose FX/DX initially because of how many nonsensical MFT vs. APS-C arguments I found trying to answer this question on Google. As I guess I should've expected, people are passionate about this stuff.


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## JerryLove (Oct 16, 2014)

Braineack said:


> With a FX using a 55mm @ f1/6 with the distance to subject at 10ft, the total DOF is around 12ft.
> With a DX (1.5x) using a 55mm @ f1/6 with the distance to subject at 15ft, the total DOF is around 18.5ft.
> With a 4/3 (2.0x) using a 55mm @ f1/6 with the distance to subject at 20ft, the total DOF is around 25ft.


With distance, not sensor size, being the deciding factor. 

DoF is not directly affected by sensor size. DoF is affected by distance to subject, and sensor size may influence the distance at which you shoot (since your angle of view is different).


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## Braineack (Oct 16, 2014)

however, according to fun online calculators:

let's say the two of us are standing 20ft from a beautiful subject.

I'm using my D600, you: a D7100.

I have my on body a 105mm 2.8 prime, and you: a 70-200 2.8--set to 70mm.

We both shoot from the same spot (distance of 20ft) and both using f/8.

I'll still only have 5.3ft of DOF, while you'll have 8.2ft...

The images will look more or less exactly the same (since 70mm is 105mm is 1.5x.), but for DOF.


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## CameraClicker (Oct 16, 2014)

Braineack said:


> however, according to fun online calculators:
> 
> let's say the two of us are standing 20ft from a beautiful subject.
> 
> ...



Many of the on-line calculators have a problem.  They suggest the same prime lens on different bodies FF and APS-C for instance will have different DOF if the camera and subject do not move and aperture is the same.  

I have full frame and APS-C bodies, and prime lenses, so I got out a tripod, a target and a tape measure.  Sensor size has no effect on DOF.

Sensor size lets you move the camera to frame the scene to match the other body... which changes the parameters that affect DOF.  That's a totally different experiment.  You can put a 10 mm lens on an APS-C Canon body and a 16 mm lens on a Canon full frame body, and the framing will look the same.  View both at 100% and the differences become evident.  If you have two APS-C bodies with different photo site densities, you can play other games too.  Much attention has to be paid to how the question is framed, and how the reply is framed, or the results can be misleading.


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## Alexr25 (Oct 16, 2014)

CameraClicker said:


> Many of the on-line calculators have a problem.  They suggest the same prime lens on different bodies FF and APS-C for instance will have different DOF if the camera and subject do not move and aperture is the same.


The major factors influencing depth of field are focal length, aperture and subject distance but there will indeed be a different DoF  for different sensor sizes because the circle of confusion is a function of film or sensor size.  The difference will not be great and will tend to slightly lessen the increased DoF due the increased subject to lens distance when shooting with a crop sensor. 
So I would have serious reservations about any DoF program that DID give the same DoF with the same lens, f stop and distance setting but different sensor sizes.


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## Braineack (Oct 16, 2014)

But that factors in a diamter limit of the sensor.  The APS-C is litterally a crop, so  that vaule should match that of an FX sensor should it not?

if I took a pictures, and literally swapped out the FX sensor for a DX, and using the exact same settings, took another picture the DOF should be identical--I just don't collect all the image information that went beyond the sensor diameter.

if 
	

	
	
		
		

		
			




where c = CoC
then c, regardless of DX or FX, should be identical.


Which is the case since 5.3ft of DOF is exactly 65% of 8.2ft.

and the CoC of a DX sensor is 0.019mm vs 0.029mm of an FX, or that same 65% difference...


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## CameraClicker (Oct 16, 2014)

Alexr25 said:


> CameraClicker said:
> 
> 
> > Many of the on-line calculators have a problem.  They suggest the same prime lens on different bodies FF and APS-C for instance will have different DOF if the camera and subject do not move and aperture is the same.
> ...


This is an example of what I was referencing.  Photo site size may indeed have an effect on DOF.  But, I have a full frame body and an APS-C body that has virtually the same size photo sites.  I have another APS-C body where there are over twice the photo sites, so I expect those photo sites are much smaller. When I did the test, I used the newer APS-C body with more photo sites.  Differences in DOF were less that errors in focusing, so not worth worrying about.  I decided to do the test when it was pointed out that one of the on-line calculators was giving results that were exactly opposite what another photographer and engineer was saying should be expected.
In electronics, 10% is considered to be "close enough" for most applications.  Sometimes that is not true, and you can get components, usually military grade, that are more expensive and have tighter tolerances.  The DOF difference was well under 10%, so not worth worrying about.


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## Derrel (Oct 16, 2014)

Despite an egregiously erroneous statement above, the smaller the sensor or film size, the greater the depth of field at each picture angle. According to a published article written by Herbert Keppler, editor of Modern Photography magazine, KODAK, in fact, literally INVENTED the very small "Kodak disc film" format, as a way to achieve hyperfocal depth of field with a lens that had its focus permanently set to about three feet. Using the then-popular 126 cartridge and 110 cartridge cameras, many snap-shooters were taking out of focus close-up shots. In order to achieve exceptionally deep, expansive depth of field, Kodak engineers determined that the only solution was to MAKE an ALL-NEW, INCREDIBLY SMALL film format! And so they did. They named it the "*disc format*". It's important to understand this point: Kodak created an all-new, ultra-small film format and cameras to go with it, in order to create a camera that offered huge depth of field from very close, to Infinity. Despite the small size of 110 film, there was not enough depth of field at close distances with fixed-focus lenses, so the solution was to follow the laws of optics, and decrease the film size and decrease the lens length, to get a normal picture angle of view AND expansive, deep depth of field. "Science".

110 film used 13mm x 17mm frames and was introduced by Kodak in 1972. Disc format was introduced a decade later, in 1982, and used 8mm x 11mm frames. The simple practical upshot is that if one wants to achieve tremendous depth of field, where things from very close to very far away are rendered in good focus, the easiest way to do that is to use a camera with a very small sensor, with its commensurately short focal length lenses. This is why smart phones, with their exceedingly short focal length lenses and tiny sensors, are able to create images with exceptionally deep depth of field. For social photography, there is a significant advantage to using a SMALL-sensor digital camera, which will allow the photographer to shoot close-in, social photography scenes that have deep depth of field, so that focusing super-critically, yet still suffering from inadequately deep focus, becomes less an issue than it was with say, a medium-format rollfilm camera, or a 35mm or "135 film format" camera, etc..

Medium format 6x6 cm rollfilm cameras with their so-called *normal lens*, which is 75mm or 80mm in length, have relatively shallow depth of field with their normal lens. Even the 65mm semi-wide-angle lens on 6x6cm film format has fairly limited depth of field. By contrast, an iPhone 5 has tremendous depth of field with its semi-wide-angle lens--even when the lens is at a wide aperture like say, f/2.4.

Let's get this clear: when making *pictures that have the same angle of view*,* the smaller* the film or sensor format,* the MORE depth of field there is at equivalent apertures*. Do the experiment yourself using your smartphone and your d-slr. If you have ever owned and shot a medium-format rollfilm camera you will KNOW, from actual experience that its "normal lens" creates shallow depth of field images at ranges inside of 40 feet, and that if you want to get more, actual, real, workable depth of field, that you want to move down to a camera that shoots to a smaller-sized capture format.


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## CameraClicker (Oct 16, 2014)

Derrel said:


> Despite an egregiously erroneous statement above, the smaller the sensor or film size, the greater the depth of field at each picture angle. According to a published article written by Herbert Keppler, editor of Modern Photography magazine, KODAK, in fact, literally INVENTED the very small "Kodak disc film" format, as a way to achieve hyperfocal depth of field with a lens that had its focus permanently set to about three feet. Using the then-popular 126 cartridge and 110 cartridge cameras, many snap-shooters were taking out of focus close-up shots. In order to achieve exceptionally deep, expansive depth of foeld, KOdak determined that the only solution was to MAKE THE FILM FORMAT INCREDIBLY SMALL!!!! and so they did.
> 
> 110 film used 13mm x 17mm frames and was introduced by Kodak in 1972. Disc format was introduced a decade later, in 1982, and used 8mm x 11mm frames. The simple practical upshot is that if one wants to achieve tremendous depth of field, where things from very close to very far away are rendered in good focus, the easiest way to do that is to use a camera with avery small sensor, with its commensurately short focal length lens. This is why smart phones, with their tiny lenses and tiny sensors, are able to create images with exceptionally deep depth of field. For social photography, there is a significant advantage to using a SMALL-sensor digital camera, which will allow the photographer to shoot close-up scenes that have deep depth of field, so that focusing super-critically becomes less an issue than it was with say, a medium-format rollfilm camera, or a 35mm or "135 film format" camera, etc..
> 
> ...



Yep!  Exactly the deal with a cell phone camera, and many point & shoot cameras.  Super tiny sensor, or film, super short lens.  A very short hyperfocal distance, almost everything is always in focus.  They are trying to get the angle of view you might get from 35 mm or 50 mm, on an SLR.  

But if you hold every variable, except the sensor size, you can see the effect of just changing sensor size.  No effective difference.


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## WayneF (Oct 16, 2014)

CameraClicker said:


> But if you hold every variable, except the sensor size, you can see the effect of just changing sensor size.  No effective difference.



You're making a joke?  You cannot possibly hold every variable the same.  If focal length and distance are the same, the lens can be the same, but the cropped view is still 1/3 smaller (FX to DX), not at all the same picture.  To have any meaning, we do need to compare like pictures. We could crop the larger sensors image smaller so we could compare, I guess.  You could be right then.   LOL

Plus the smaller frame requires greater enlargement, which affects CoC, which affects DOF calculation.   DOF is not an absolute from the lens, the overall concept simply depends on how you enlarge it to view it. The normal DOF calculation always assumed an 8x10 print viewed from 10 or 12 inches (standard conditions).  It is about what we see.  CoC is the dot the eye can see, when enlarged to the same print size.   The smaller cropped sensor suffers that way.

The smaller cropped sensor is considered to have greater depth of field because we do NOT keep everything the same.  We only keep the image the same.  This same view requires either a shorter lens (more DOF), or standing back farther (more DOF).


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## Derrel (Oct 16, 2014)

The smaller the capture format, the shorter the focal length needed for a given angle of view. The smaller the format, and the shorter the lens, the shorter the focus distance needed to achieve hyperfocal depth of field. A very good article on depth of field and sensor size was written a few years back by Bob Atkins.Depth of Field, Digital Photography and Crop Sensor Cameras - Bob Atkins Photography

*This is probably the single best article on the subject I have seen*. What's important to note, and Bob notes this, is that depth of field does not increase or decrease in a simple, linear manner! Look about 3/4 of the way down the page, to the chart that has the light aquamarine, lime green, and then lavender-colored segments!!!!  DOF examples are broken down into three zones: Close-up; intermediate; and distances close to the hyperfocal distance.

His chart shows APS-C, FX or 35mm, and 6x9 cm film format, and charts out the depth of field for a 46-degree angular field of view, across all three formats, at close-up range (0.15 meters), intermediate distance of 2.0 meters, and at  5.0 meters.

Once again, this article is comparing three distinct sizes or "formats", ALL with the lens required to give a 46 degree angular view. It's a simple fact: moving to a smaller film or smaller digital sensor format increases depth of field at close-up range, at intermediate ranges, and at longer distances. And the important thing to note is this article is charting out the depth of field differences with all three camera formats using their size-appropriate "normal lens" length!

As Wayne mentioned, we need to compare *similar pictures*, made with different camera formats and different lens lengths*. *That is what this article helps people understand.


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## CameraClicker (Oct 16, 2014)

WayneF said:


> CameraClicker said:
> 
> 
> > But if you hold every variable, except the sensor size, you can see the effect of just changing sensor size.  No effective difference.
> ...



No sir, not joking.  Sure you can keep all the variables the same!  Put the camera on a tripod.  Shoot down a hallway.  Use a stationary target.  Use some basic measuring equipment.  Light with strobes if necessary.

I spent a career doing engineering, mechanical, electrical and software.  If you want to understand a system, keep everything the same except what you want to study.  Then see the effect of that change.  That is a pretty standard method of dealing with complicated systems.  I'm sure you even use that method yourself sometimes when setting up strobe lighting?  Set the first light, get it the way you want.  Turn off that light, set the next light get it the way you want.  Repeat for the other lights.  Once they are all set, turn the lights back on and take your photo.  Sound familiar?

When I got my first dSLR it was a 30D, and I was told the smaller sensor size would increase the effective length of the lens!  At the same time, I was shown an Olympus that had a crop factor of 2, so it was supposed to make a 200 mm lens look like 400 mm!  If you don't worry about framing and instead you look at each photo at 100%, you see what nonsense that is.  

An 8 X 10 may make a degree of sense when dealing with portraits.  It may also make some sense if you have a full frame Nikon and and APS-C Nikon and both have the same number of pixels.  As you move to other brands and newer models, pixel counts are all over the map, as are photo site sizes.  Cropping may also nullify the 8 X 10 argument.  The point remains that while you may use an APS-C body differently than a full frame body, any change in DOF from the sensor itself will be extremely small or non-existent, while changes in DOF from moving closer or further away will be noticeable.  Not everyone limits their photography to portraits and understanding what is really affecting your photos, and why, can be quite useful.


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## WayneF (Oct 16, 2014)

CameraClicker said:


> No sir, not joking.  Sure you can keep all the variables the same!  Put the camera on a tripod.  Shoot down a hallway.  Use a stationary target.  Use some basic measuring equipment.  Light with strobes if necessary.



No, you changed the sensor size.  That's a big deal, a new game then.  You cannot just ignore it.   You surely don't imagine tiny compact camera sensors are the equal of full frame DSLR sensors?



> I spent a career doing engineering, mechanical, electrical and software.  If you want to understand a system, keep everything the same except what you want to study.  Then see the effect of that change.  That is a pretty standard method of dealing with complicated systems.  I'm sure you even use that method yourself sometimes when setting up strobe lighting?  Set the first light, get it the way you want.  Turn off that light, set the next light get it the way you want.  Repeat for the other lights.  Once they are all set, turn the lights back on and take your photo.  Sound familiar?



Who didn't?    But we do have a tendency to imagine our own solutions, imagine how it "ought" to work,  making up how we would have done it, and then trying to tell everyone how it actually works that way.  Not always true though, esp in an unknown field, but you can learn to break that habit.     First step is to think back "how am I certain this is true?".

You're overlooking a major variable, sensor size.  Just a little bit of of study can make it very clear, this stuff is all very well known.  You just have not started learning yet.  You are still imagining your own solutions, which are rather incomplete.



> When I got my first dSLR it was a 30D, and I was told the smaller sensor size would increase the effective length of the lens!  At the same time, I was shown an Olympus that had a crop factor of 2, so it was supposed to make a 200 mm lens look like 400 mm!  If you don't worry about framing and instead you look at each photo at 100%, you see what nonsense that is.



Of course the lens cannot and does not change by just putting it on some camera body.   No one thinks the lens changes.

But the cropped sensor does crop that lens view, it only sees a smaller cropped view.  With the same lens at same distance, the cropped sensor only sees a narrow view, same view as the uncropped sensor would see with a lens longer by the crop factor.... 1.5x or 1.6x longer focal length.  This view comparison is so that users familiar with 35 mm film (It was very popular for more than 50 years), know what the contraption is going to do. This crop factor is called Equivalent Focal Length, and it describes the cropped view, as relative to the uncropped, only important because it compares to the old familiar 35mm film sensor size.  Then old timer 35mm film users know what a 100 mm lens does on a cropped sensor... the cropped view it sees mimics a 1.5x or 1.6x longer lens on the uncropped sensor.  And it does mimic a telephoto view (if as seen on uncropped).   Any cropping (any image, any time later in a photo editor) shows this same telephoto effect when enlarged back to same size.  It's all well known.

Different film sizes worked exactly the same way too - It was all well understood way back then too. However it was uncommon to be able to use the SAME lens on different film sizes (we could at least try in darkroom enlargers). But it is why film sizes normal lens focal length varied with their film diagonal dimension. Equivalent focal length concept. Same thing. Same thing with DOF too.  Smaller film size has greater DOF (but less effective resolution when enlarged more)..   Remember Ansel Adams 1930s F/64 Group?  This was trying to get sharper images on the 8x10 film size.  This has all been well known for many decades.  Digital is about the only thing new.   Newcomers have to get up to speed with the facts first though.



> An 8 X 10 may make a degree of sense when dealing with portraits.  It may also make some sense if you have a full frame Nikon and and APS-C Nikon and both have the same number of pixels.  As you move to other brands and newer models, pixel counts are all over the map, as are photo site sizes.  Cropping may also nullify the 8 X 10 argument.  The point remains that while you may use an APS-C body differently than a full frame body, any change in DOF from the sensor itself will be extremely small or non-existent, while changes in DOF from moving closer or further away will be noticeable.  Not everyone limits their photography to portraits and understanding what is really affecting your photos, and why, can be quite useful.



It makes full sense to anyone that learns the actual facts instead of making up their own notions.  * It is NOT at all about pixels.*  Pixels merely attempt to digitally reproduce the analog lens image.  The best job pixel resolution can do is to reproduce the lens image resolution well (pixels cannot make it better, or even as good - even if we ignore Bayer, there is Nyquist, etc). The overall concept is about the analog lens image projected onto the sensor, which we hope to copy well.   Cropping makes that source image smaller, which then requires more enlargement to appear equal again, and we all know enlargement is a resolution disadvantage. Variable CoC with sensor size accounts for that, and affects DOF.

And DOF is certainly Not an inherent property just of the lens as you imagine.   Focal length, aperture, and subject distance are factors, *as is sensor size and the subsequent enlargement necessary to see it*.   Cropped sensors require more enlargement to compare at same size.  DOF details have been known for at least 100 years.
It is really not a Day One subject for the newbies however.

The issue is that you're simply believing your own wrong assumptions (imagining DOF must only be about the lens).  It just proves you have done no study.  You really need to do a bit of study about how things work if you're going to try to explain how things work.  It becomes pretty funny publicly otherwise.  This stuff is all very widely known.


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## Derrel (Oct 17, 2014)

Dude--sensor size, or film size, plays a HUUUUUUUUUUUUUUGE role in the lenses used, and the depth of field possible. Anybody who does NOT understand that smaller sensors have deeper depth of field than larger and larger sensors or larger and larger film sizes really does NOT understand the way cameras and their lenses actually function.

How about this: read Wayne's post carefully. Then, spend a few minutes and check out the FACTS, and then please, go through and kill-file your erroneous nonsensical posts made in this thread. It's no wonder people never can learn the basics when so much B.S. is put forth with so much earnestness and sincerity.

Background blur and its relationship to sensor size: Digital Photography Review

Please avail yourself of the very clear, simple chart: Tabelle_2.png


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## theraven871 (Oct 21, 2014)

I have read so many articles on this.
YES, there IS a difference.   I'll simplify.

Your crop factor (on APS-C) applies not only to the focal length, but also to the aperture as well.
Thus, lets for argument sake say we want to purchase the equivalent of a 24-70mm f2.8 on a CROP sensor body.
Most people will tell you the 17-50mm f2.8 is identical.  This is because a 1.5x crop on 17-50 is roughly 24-70mm.
What they DON'T tell you is that you also need to multiply the aperture. 

So, for this example, a 17-50mm f2.8 is NOT equal to a 24-70mm f2.8.
When all the math is done, a 17-50 f2.8 is very close to a 24-70mm *f4.
*
Of course, this math applies to all crop sensor lenses.
A 70-200mm f2.8 lens on a crop sensor body becomes a 105-300mm f4.
A 50mm F1.8 becomes a 75mm f2.8

And so on....
You just simply need to multiply BOTH your focal range AND aperture by your crop factor
(Crop factor is 1.5x for Nikon and 1.6x for Canon).


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## Braineack (Oct 21, 2014)

are you suggesting the exposure changes between the two?


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## Derrel (Oct 21, 2014)

Braineack said:


> are you suggesting the exposure changes between the two?



I think he's suggesting the well-known "equivalence" concept that the smaller sensor's greater depth of field requires a wider aperture at each and every equivalent field of view, to get equal defocused background or equal depth of field. This is pretty well known and accepted.


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## Braineack (Oct 21, 2014)

okay.  the difference is 65% less (DX to FX) DOF then, which I did do the math for in post #15.

seems to be direct relationship in the difference between the CoC area and the difference in DOF.


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## WayneF (Oct 21, 2014)

theraven871 said:


> I have read so many articles on this.
> YES, there IS a difference.   I'll simplify.
> 
> Your crop factor (on APS-C) applies not only to the focal length, but also to the aperture as well.
> ...




Wording is very misleading. wrong as stated.  The problem is this means to speak only of DOF, but it never mentions DOF to specify that single meaning.  It seriously needs more careful wording.

f/2.8 aperture is f/2.8 aperture, exposure-wise on any camera, of any size or crop, or uncropped.  There is not  any "equivalent" f/2.8.  It either is, or it isn't.    

However apparent DOF does increase on smaller cropped sensors.  A 16mm lens does have a greater DOF than 24mm.   To compare at the same field of view, the smaller sensor either has to use a longer lens (greater DOF) or if with same lens, they have to stand back farther (greater DOF), to see the same view, to allow any comparison. But it requires lens extension or a teleconverter to change f/2.8 to be f/4.


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## theraven871 (Oct 21, 2014)

Derrel said:


> Braineack said:
> 
> 
> > are you suggesting the exposure changes between the two?
> ...



Exactly.  My point was that a Full Frame lens on an APS-C sensor will produce less "depth of field" than with a full frame sensor.
This is because the Aperture is not the same on different sensors (using Full Frame as a reference point).

Where things start to get even more confusing is the focal range has also changed.  
If you were focused on a subject 10 feet away at 50mm on a full frame
(then took that same lens on a crop sensor)
You will then need to step backwards to keep the same composition.  I don't know the math off the top of my head, but then you may be somewhere near 12 feet away.
Not only did the aperture change from the crop sensor, but now since the distance to the subject changes, the DoF also changes.

So, if I'm looking at this correctly, their are TWO factors which will create a wider depth of field on a cropped sensor. 
The fact that your aperture will multiply based on your cropped ratio (1.5x or 1.6x) AND that you need to change the distance to your focus point.


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## astroNikon (Oct 21, 2014)

So to be equivalent
does the 17-50 need to be a f/1.4
to be equivalent to a 24-70/2.8 ?


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## WayneF (Oct 21, 2014)

theraven871 said:


> Exactly.  My point was that a Full Frame lens on an APS-C sensor will produce less "depth of field" than with a full frame sensor.
> This is because the Aperture is not the same on different sensors (using Full Frame as a reference point).



No, the aperture certainly does not change on a cropped sensor.  Neither does the focal length (of the same lens).  A lens does not change in any way by putting it on a cropped sensor.  Only its field of view is reduced when the smaller sensor crops it.

The  DOF Reason (greater DOF of cropped sensors) is simply because the lens focal length, or the place where we have to stand, has to change for the DOF of a cropped sensor *to see the same view* as uncropped.


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## theraven871 (Oct 21, 2014)

Start watching around the 20 minute mark.


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## theraven871 (Oct 21, 2014)

Mathematically, your "equivalent" aperture DOES change when you mount a full frame lens on a cropped sensor.  The sensor isn't as wide as the full frame sensor.
Aperture is the relationship of the width or opening of the lens to the length.
So a f2.8 lens is mathematically identical if you mount it on a full frame or Crop sensor.  At least when speaking of the lens itself.  The image sensor however lowers the diameter which changes the aperture. 
So, a full frame 70-200 f2.8 lens will function like it was a f4 lens on a crop sensor.  This is because the sensor size is smaller.
The APS-C (cropped) sensor is not utilizing the entire diameter of the lens.  Thus, the math changes. 
A crop sensor basically narrows the diameter of a "full frame lens" because there is unused space.


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## WayneF (Oct 21, 2014)

theraven871 said:


> Mathematically, your "equivalent" aperture DOES change when you mount a full frame lens on a cropped sensor.  The sensor isn't as wide as the full frame sensor.
> Aperture is the relationship of the width or opening of the lens to the length.
> So a f2.8 lens is mathematically identical if you mount it on a full frame or Crop sensor.  At least when speaking of the lens itself.  The image sensor however lowers the diameter which changes the aperture.
> So, a full frame 70-200 f2.8 lens will function like it was a f4 lens on a crop sensor.  This is because the sensor size is smaller.
> ...


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## CameraClicker (Oct 21, 2014)

Well, it looks like the discussion has continued while I have been occupied by automobile issues.  It also appears as though the understanding within the group of respondents may be about as good as it is among those to whom I have spoken in person.  I think a fact is something that can be demonstrated/proven by observation/experimentation.  I don't have an axe to grind and I may well be wrong.  It wouldn't be the first time, it won't be the last, either.

This is what I wrote previously:  "
Many of the on-line calculators have a problem. They suggest the same prime lens on different bodies FF and APS-C for instance will have different DOF if the camera and subject do not move and aperture is the same.

I have full frame and APS-C bodies, and prime lenses, so I got out a tripod, a target and a tape measure. Sensor size has no effect on DOF.

Sensor size lets you move the camera to frame the scene to match the other body... which changes the parameters that affect DOF. That's a totally different experiment. You can put a 10 mm lens on an APS-C Canon body and a 16 mm lens on a Canon full frame body, and the framing will look the same. View both at 100% and the differences become evident. If you have two APS-C bodies with different photo site densities, you can play other games too. Much attention has to be paid to how the question is framed, and how the reply is framed, or the results can be misleading."

So, during some limited free time this week, I stuck a target on a stool.  Put a Sigma 150 mm f/2.8 macro lens on the tripod, and took photos with two different APS-C bodies and a full frame body.

Some random web page that had dimensions said:  APS-C is 22.2 x 14.8mm (Full Frame is 36 x 24mm).  I don't know without looking in a manual if that is the correct measurements, but it suggests APS-C sensors are about half the size of a full frame sensor.  If there is anything to the argument that moving from APS-C to full frame , without doing anything else, affects DOF, it should be readily apparent.

Here are 3 photos, screen captures, to ensure all EXIF data was removed.  Which photo is from which body?



  
........................... A ..................................................... B ............................................................... C ................................

These were all taken through the same lens, at the same aperture, at the same distance.  If you see an obvious difference, please tell me which of A, B or C is from the full frame body.


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## theraven871 (Oct 21, 2014)

I believe the confusion comes from how lenses are rated.
They are rated using the 35mm format.  So a 17-50mm f2.8 is only a 17-50mm f2.8 when mounted to a FULL FRAME (35mm) sensor.
When you mount a 17-50 f2.8 to a crop sensor, it functions as if it were the 35mm equivalent of a 24-70 f4 (approx)

Crop sensor lenses are NOT rated using the crop sensor format (What is it? 21mm???).  
They are still rated using the 35mm format, which makes them appear more desirable.  This is deceiving to consumers.  
This is why Full Frame sensors produce different imagines.    

Can you tell the difference between f2.8 and f4?  That's a different discussion...


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## theraven871 (Oct 21, 2014)

CameraClicker said:


> Well, it looks like the discussion has continued while I have been occupied by automobile issues.  It also appears as though the understanding within the group of respondents may be about as good as it is among those to whom I have spoken in person.  I think a fact is something that can be demonstrated/proven by observation/experimentation.  I don't have an axe to grind and I may well be wrong.  It wouldn't be the first time, it won't be the last, either.
> 
> This is what I wrote previously:  "
> Many of the on-line calculators have a problem. They suggest the same prime lens on different bodies FF and APS-C for instance will have different DOF if the camera and subject do not move and aperture is the same.
> ...


Going to take a guess here.   Is A the full frame?


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## WayneF (Oct 21, 2014)

WayneF said:


> theraven871 said:
> 
> 
> > Mathematically, your "equivalent" aperture DOES change when you mount a full frame lens on a cropped sensor.  The sensor isn't as wide as the full frame sensor.
> ...




No, this is getting worse.     f/stop is focal length / aperture diameter.  It is NOT even about the sensor. the lens does not change in any way when placed on any camera.  That would be a silly notion.

Nor does the focal length change if on a cropped sensor.  You need to realize what Equivalent focal length actually means.

Assuming same lens is used, at same distance, all that a cropped senor changes is the field of view.   The reasoning is:   The cropped sensor sees a smaller cropped view, a more narrow view than if uncropped.  That is what cropped refers to.  But to compare it, we can only compare the same size image of the same view on both sensors. To do this (to see the same view), the uncropped sensor would need to use a lens longer than the uncropped sensor.  Compared to the uncropped view, that same lens (cropped smaller by smaller sensor) superficially appears as if a longer lens, so which the uncropped needs now to see the came cropped view.  That longer lens on uncropped sensor is called the Equivalent (view) of the cropped sensor (which is as is). The term Equivalent applies to the uncropped sensor.

The ideas is, if you crop ANY IMAGE,  ANYTIME LATER in your editor, and then enlarge it back to compare as the same size again,  that enlargement appears as a psuedo telephoto view (as if a longer lens).  Same applies the the smaller cropped sensor too.  But instead, all it is a smaller cropped image, enlarged more later.


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## theraven871 (Oct 21, 2014)

WayneF said:


> WayneF said:
> 
> 
> > theraven871 said:
> ...


A cropped sensor can NOT utilize the entire diameter of the 35mm lens.
Thus you have to apply (multiply) the crop factor to BOTH the aperture and the focal range.

Following your logic, my iPhone (with a 2.0 aperture) will have the same bokeh as a full frame Nikon at the same focal range.
We ALL know that isn't true.

You are correct that a cropped sensor changes the field of view.    But a cropped sensor DOES affect the aperture rating.
If you have a 100mm lens, with an iris (diameter) of 25mm, you have a 100mm f4 lens - On 35mm ONLY.
Since a crop sensor camera cannot use the full opening (in this example it is 25mm) you apply the crop factor to the aperture as well as the focal range.
Aperture ratings are based on 35mm.  NOT cropped sensors.

Otherwise, if what you're saying is true, all these "point and shoot" f2.8 cameras out there with crop factors of 3x, or 4x would produce the same bokeh as a 2.8 lens mounted on a 35mm (full frame) camera.   Everyone knows that isn't the case.
C'mon buddy.  We are talking basic math here.   The entire formula for how aperture is determined is based on a 35mm format.  The moment you change that format, you have to apply the same ratio to both the focal range and the aperture to find the 35mm equivalent.   The point you seem to be missing is that a 17-50mm f2.8 lens for an APS-C camera is NOT rated for an APS-C camera/sensor.  That rating is still based on 35mm or full frame.   The moment you mount that 17-50mm lens on a cropped sensor, it will function as the 35mm or full frame equivalent of a 24-70 f4.  
I'm not saying its not a 2.8 lens.  I'm saying the formula you're basing it on has to change. 
So, if you're comparing only cropped sensors to cropped sensor lenses, its not confusing.  But if you're attempting to say compare a lens for a cropped sensor to the 35mm (full frame) equivalent, you will find that my math is correct.  You not only multiply the focal length to the crop factor, you also multiply the aperture by the crop factor.  If you change the focal length (becuase you're mounting to a crop sensor) you also change the aperture.  Aperture is determined by focal length.  You cannot change it without affecting the aperture. 
I understand you're looking at this from someone just thinking you're digitally cropping into an image.  But the aperture value is also changed. 
This isn't as noticeable on the APS-C format.  But if you think I'm lying, look at cameras with a f2.8 lens with a 3x or 4x crop.


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## WayneF (Oct 21, 2014)

theraven871 said:


> WayneF said:
> 
> 
> > WayneF said:
> ...




Not very clear obviously.  OK, I don't care what wrong stuff you want to think.  I was just reacting to someone on the internet being so wrong.       It just seems harmful to others to spread it around publicly though. 

The iPhone (5S) has a focal length of 4.2mm. I think crop factor is about 7x, a senor size almost too tiny for numbers.     That is the effect you discuss.


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## CameraClicker (Oct 21, 2014)

I don't know if this will help, or just muddy things further.
Here are a couple of size reduced frames
  

Full Frame sensor .......................................... APS-C sensor

  

Full Frame 100% crop ............................................APS-C 100% crop


On the full frame body, 16 mm lens.  On the APS-C body, 10 mm lens.   For the whole frame, the field of view looks the same, except I didn't aim perfectly.

So, you might conclude 10 mm on APS-C equals 16 mm on full frame.  But if we grab 700 px by 500 px at 100% out of each frame, and I tried to use the mail truck's bumper and the white vertical line as my reference, we see 16 mm is longer than 10 mm, which is what we would expect since the crop is done by having less sensor in the image circle.

Likewise, if you have a 100 mm lens with an aperture of f/2.0, that's a huge aperture of 50 mm!  If you have a 4 mm lens with an aperture of f/2.0, that's not so big, at 2 mm.

Small sensor bodies, like almost any P&S under 2 or 300 dollars, have very short lenses.  Cell phones have about 4 mm.  P&S typically between 4 mm and 6.5 mm at the wide end.  The sensor is so small, you get a regular field of view, but the focal length is very short, so getting bokeh is fairly difficult because the hyperfocal distance for 4 or 6.5 mm is somewhere less than 3 feet.  Everything is always in focus.  True, some of the P&S cameras like a Canon G11 have fairly large apertures available, Rockwell's page states "6.1~30.5mm f/2.8-4.5.", it is possible, but you have to work at it, to get something out of focus.  

Last thought for now:  If you have a full frame sensor and 100 mm lens, and you set f/5.6, and you have enough light for a given exposure at say, 1/200th.  Changing the sensor will not affect any of that if you don't move.  If it did, you would have a problem getting an even exposure across a full frame sensor.


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## Braineack (Oct 21, 2014)

theraven871 said:


> Start watching around the 20 minute mark.



This is the same guy the reviewed the D810, and loved it in every respect but couldn't ditch Canon because he thinks inferior products are better.

*His math is flawed: *The focal length never changed.

 therefore there's no need to change the equation. He changed the definition of aperture being N = f/D to N = (f x crop factor) / D

This is seriously one of the more retarded thing i've seen all day; and I work for the government.


also aperture does not equal DOF.

I put the mathematical formula for DOF in post #15.  where the subject distance, focal length, aperture, and CoC all come into play.

Aperture determines the angle of light rays that can pass through to the sensor.  It's a factor of a lens, and it's fixed--whatever camera body you bolt it to doesn't not change this value.  It's written in stone.


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## Ysarex (Oct 21, 2014)

Derrel and Wayne are correct and Braineack's math is correct. In an appropriate comparison of like photos smaller sensor cameras produce more DOF.

To make any meaningful comparison in this discussion you must make a comparison of similar photographs. The content and perspective in the two compared photographs must be identical as must also be the photographic conditions -- same exposure, which means same f/stop etc. Therefore both photographs must be taken from the exact same location and the angle of view of the camera/lens systems must be adjusted to produce identical content. Both photographs must be taken using the same photographic conditions, i.e. exposure. All other comparisons are worthless.

Comparing like photographs using different format cameras a photo taken with a smaller format sensor will have more DOF than the same photo taken with a larger format sensor.

..........f^2
H = ----------
..........Nc

The above equation is standard. If you dispute it then you're denying accepted math and are certifiable.

"H" is hyperfocal distance, "f" is focal length, "N" is f/stop and "c" is circle of confusion. It is likewise accepted math that c is determined by the size of the format. If you think sensor size does not effect DOF please show examples of this equation in which changing "c" has no effect on "H."

If you do the math for the above equation so that two different format cameras are taking the exact same photograph you get different values for "H" proving mathematically that you get more DOF from a smaller sensor camera. The math in the illustration below is correct. Hyperfocal distance for the 7D is closer to the camera and that means there's more DOF.

Joe


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## Braineack (Oct 22, 2014)




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## theraven871 (Oct 22, 2014)

Braineack said:


> theraven871 said:
> 
> 
> > Start watching around the 20 minute mark.
> ...



He didn't say he thought inferior products were better.  He never said Canon was better. 
He wanted to switch to Nikon but stated that the Nikon 70-200 has a focal breathing problem.  Whereas the Canon 70-200 lens does not.
He stated that the 70-200 lens he uses too much and felt the focal breathing issue presented a greater issue than gaining the benefits of switching to Nikon.


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## Braineack (Oct 22, 2014)

theraven871 said:


> He didn't say he thought inferior products were better.  He never said Canon was better.
> He wanted to switch to Nikon but stated that the Nikon 70-200 has a focal breathing problem.  Whereas the Canon 70-200 lens does not.
> He stated that the 70-200 lens he uses too much and felt the focal breathing issue presented a greater issue than gaining the benefits of switching to Nikon.



The Canon 70-200 exhibits the same breathing "issue" and Matt Granger has illustrated Canon is actually the worst between the Nikon, Canon, and Tamron versions as far as focus-breathing is concerned.

I was also hyperbolizing.


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## theraven871 (Oct 22, 2014)

Ysarex said:


> Derrel and Wayne are correct and Braineack's math is correct. In an appropriate comparison of like photos smaller sensor cameras produce more DOF.
> 
> To make any meaningful comparison in this discussion you must make a comparison of similar photographs. The content and perspective in the two compared photographs must be identical as must also be the photographic conditions -- same exposure, which means same f/stop etc. Therefore both photographs must be taken from the exact same location and the angle of view of the camera/lens systems must be adjusted to produce identical content. Both photographs must be taken using the same photographic conditions, i.e. exposure. All other comparisons are worthless.
> 
> ...



You just compared two different lenses on two different sensors.
If you compare a 50mm prime on a full frame sensor and a 50mm prime on a cropped sensor, look at the DEPTH OF FIELD.
Even at the same aperture, the depth of field will be smaller on the full frame.
That's all I'm trying to say.
I'm not talking about full frame vs APSC lenses.   I'm talking about the same lens on different sensors.


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## theraven871 (Oct 22, 2014)

Braineack said:


> theraven871 said:
> 
> 
> > He didn't say he thought inferior products were better.  He never said Canon was better.
> ...


I'm glad you pointed this out.  I looked and found Matt's video where he demonstrated this.
I'm looking to switch to Nikon and this helps my confidence.


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## Ysarex (Oct 22, 2014)

theraven871 said:


> Ysarex said:
> 
> 
> > Derrel and Wayne are correct and Braineack's math is correct. In an appropriate comparison of like photos smaller sensor cameras produce more DOF.
> ...



I compared *the same photograph* taken with two different cameras (sensor sizes). A comparison that would be interesting and meaningful to a photographer.

You can't take *the same photograph* with a 50mm lens on a FF camera and also a cropped sensor camera. So if you compare an apple with an orange and proclaim that they're different what was the point of your comparison? My niece would say, "duuuuhhhhhh."

Joe


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## theraven871 (Oct 22, 2014)

Ysarex said:


> theraven871 said:
> 
> 
> > Ysarex said:
> ...


My line of thinking is that you can get a 50mm 1.8 prime for both a full frame or crop sensor.
Took a photo with both @ f1.8 you will notice that the full frame has more bokeh.  
Its slight, but its there.    Is it worth spending the money for full frame?  Possibly, but probably not.
I'm wondering if I'm talking about something entirely different than everyone else.   

I'm not saying that the physical aperture of a lens actually changes when you put it on a cropped sensor.  That would require us to be in the Twilight Zone.
What I'm saying is that an identical lens will take different pictures when mounted on a full frame vs cropped sensor.
The majority of my point is that to find out what the EQUIVALENT lens would be on a full frame, you would need to multiply BOTH the focal length and the aperture by the crop factor.
Everyone seems to understand that a 50mm lens on a crop sensor will have the equivalent focal length of 75mm (if its a 1.5x crop)
My entire point was that if you shot that 50mm lens @ f1.8 on a crop sensor, the equivalent performance would be that of f2.8 .  NOT f1.8.
Thus, a 50mm 1.8 lens on a cropped sensor has very near performance to a 75mm f2.8.   Its still a 50mm 1.8, but it functions differently when on a crop sensor.
A lens on a crop sensor at f1.8 is different from a lens on a full frame sensor at f1.8.   

What is upsetting to me is that we use the same terms for both formats.  A 50mm f1.8 on a cropped sensor is a very different experience than a 50mm f1.8 on a full frame.
For marketing purposes, it would be more accurate to instead name a APSC 50mm 1.8 a 75mm f2.8 instead.  Because that's the performance you're going to get out of it.
Yes, technically speaking the lens physically hasn't changed. It just will perform differently.  That's all that matters to me. 
My point is that people want to convince consumers that a 17-50 f2.8 lens (on a crop sensor)  will perform the same as a 24-70 f2.8 (on a full fram).   That's just not true.   
Yes, the focal range will be near the same but the depth of field on the cropped lens will not be the same at f2.8 as it is on the full frame.
The depth of field on the cropped sensor lens @ f2.8 will be very close to the full frame lens @ f4.

My point is that while I admit that f2.8 on a crop sensor is still a fast aperture, sometimes you want that extra bokeh.  I buy f2.8 lenses to shoot at f2.8.   If I'm shooting at f2.8 I want the bokeh that f2.8 delivers.  Not f4.


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## Braineack (Oct 22, 2014)

theraven871 said:


> Yes, the focal range will be near the same but the depth of field on the cropped lens will not be the same at f2.8 as it is on the full frame.
> 
> The depth of field on the cropped sensor lens @ f2.8 will be very close to the full frame lens @ f4.
> 
> My point is that while I admit that f2.8 on a crop sensor is still a fast aperture, sometimes you want that extra bokeh.  I buy f2.8 lenses to shoot at f2.8.   If I'm shooting at f2.8 I want the bokeh that f2.8 delivers.  Not f4.



This was a better way to put it.

You should use the caveat "in regards to DOF" especially when speaking about aperture, which controls the exposure as well.  You didn't before and I think that's where everything fell apart.


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## CameraClicker (Oct 22, 2014)

Ysarex said:


> I compared *the same photograph* taken with two different cameras (sensor sizes). A comparison that would be interesting and meaningful to a photographer.
> 
> You can't take *the same photograph* with a 50mm lens on a FF camera and also a cropped sensor camera. So if you compare an apple with an orange and proclaim that they're different what was the point of your comparison? My niece would say, "duuuuhhhhhh."
> 
> Joe



It's only a comparison that would be interesting to some photographers.  Have you noticed we are all talking about different parts of the same thing.  Frequently we make brief statements that are true in certain circumstances, but don't really illuminate sufficiently to permit the information to be used/understood in other situations.

Bokeh comes mostly from focal length, aperture, and distance to subject/distance to background.  If a smaller/larger sensor allows you to move with respect to your subject/background, that movement will be what affects the bokeh.  Put a 50 mm f/1.8 lens on a crop body, or on a full frame body, and you will be able to go and shoot with the same ISO, same shutter speed, and same aperture, and you will get an image with the same exposure, but different framing.  If you want more bokeh, get a full frame body because for any given focal length, you can stand closer and still fit your subject in.  Get a medium format camera because the much larger sensor will let you stand even closer!  Standing closer is the part that will deliver more bokeh.  Same lens, same distance to subject, same aperture, same DOF, different framing if you have different sensor sizes.


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## CameraClicker (Oct 22, 2014)

theraven871 said:


> My point is that while I admit that f2.8 on a crop sensor is still a fast aperture, sometimes you want that extra bokeh.  I buy f2.8 lenses to shoot at f2.8.   If I'm shooting at f2.8 I want the bokeh that f2.8 delivers.  Not f4.



See, this is the thing.  Mostly I don't care about bokeh.  I want f/2.8, or even f/1.4 to be able to deliver extra shutter speed when it is dark. And, usually the prime lens I am using on a crop body is the same lens I use on a full frame body.  So an 85 mm f/1.4 lens serves equally well on both bodies since I'm not framing someone's portrait, and frequently I'm not going to move, or can't move, anyway.  But I can often crop further with either sensor.


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## astroNikon (Oct 22, 2014)

Isn't bokeh also related to the number and shape of aperture blades in the lens.
Thus another reason to use the same lens at the same aperture setting in multiple comparisons.
Since Bokeh is the out of focus points of light and not just OOF background ??


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## theraven871 (Oct 22, 2014)

CameraClicker said:


> theraven871 said:
> 
> 
> > My point is that while I admit that f2.8 on a crop sensor is still a fast aperture, sometimes you want that extra bokeh.  I buy f2.8 lenses to shoot at f2.8.   If I'm shooting at f2.8 I want the bokeh that f2.8 delivers.  Not f4.
> ...



I completely understand what you're saying.  
Sometimes you really need fast apertures, especially if you're doing any night photography.  I don't know of any exposure difference that would apply when using a crop vs full frame lens.  
However, sometimes you want a fast aperture for the stylized bokeh effect to help make portraits pop.   But bokeh is an effect only.   
If you don't care about bokeh, then my point was lost on you.


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## theraven871 (Oct 22, 2014)

astroNikon said:


> Isn't bokeh also related to the number and shape of aperture blades in the lens.
> Thus another reason to use the same lens at the same aperture setting in multiple comparisons.
> Since Bokeh is the out of focus points of light and not just OOF background ??



I believe that the number of aperture blades as well as the shape (some are more rounded) can affect the shape and "quality" of the bokeh.
But it shouldn't affect the amount.

Of course, the shape and quality is a very subjective argument.


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## Ysarex (Oct 22, 2014)

theraven871 said:


> Ysarex said:
> 
> 
> > theraven871 said:
> ...



There was a persistent error in this thread that sensor size is not a factor in determining DOF. My post here was to correct that error. What you're talking about is related but you're still sounding a bit confused with the whole equivalence concept. For example one of my favorite lenses that I used to take portraits was a 150mm f/2.8. I shot that lens on a 6x7 camera -- a 60mm x 70mm negative not a puny little 36mm x 24mm negative. I could say that I bought that f/2.8 lens to shoot at f/2.8 not the equivalent f/5.6 it would be on a FF camera. If I'm shooting at f/2.8 I want the bokeh that f/2.8 delivers -- not f/5.6.

Joe


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## CameraClicker (Oct 22, 2014)

astroNikon said:


> Isn't bokeh also related to the number and shape of aperture blades in the lens.
> Thus another reason to use the same lens at the same aperture setting in multiple comparisons.
> Since Bokeh is the out of focus points of light and not just OOF background ??



I suspect most people who want bokeh shoot wide open, so the blades are out of the way.  Bokeh is actually the quality of the out of focus parts, which is slightly different than DOF.  

Joe still hasn't convinced me that sensor size is a factor.  The way he adjusts for sensor size is the factor.


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## theraven871 (Oct 22, 2014)

Ysarex said:


> theraven871 said:
> 
> 
> > Ysarex said:
> ...


I'm not confused about the equivalence.  This is a beginners forum thread.
I want to ensure that anyone that buys a 17-50mm f2.8 lens for a crop sensor doesn't expect the exact same performance as a 24-70mm f2.8 full frame.  Too often people are comparing lenses for crop sensor cameras to their full frame counterparts.
I completely understand how medium formats compound what I'm trying to say.  (I shot Pentax 645 for years)

The point is that I see so many advertisements for cropped sensor lenses where they state something similar to: "its just like having the 24-70 with f2.8".
Its a lie.  Exposure may be similar, but the depth of field at 2.8 is different than at f4.
Most of the people I speak with buy the 2.8 lenses because they want the bokeh effect.  That's what I meant when I said "I buy f2.8 to shoot at f2.8".
I don't want someone to get the impression that the depth of field performance at f2.8 is the same on both crop or full frame.
There are differences between crop sensors and full frame.   Just the same as there are differences between full frame and medium format.
I'm only attempting to highly what the marketing teams don't state clearly.  I'm not attempting to say one format is superior to the other.
They have different performance. 

So, coming full circle.  You cannot expect a 50mm f1.8 lens to have the same performance if mounted to a crop sensor, full frame or medium format.
Despite what marketing teams what consumers to think, the format size makes a difference.

I don't even know what you're talking about anymore.  I really don't.
The title of this thread is DEPTH OF FIELD.   
Depth of field changes based on sensor size, focus distance, and aperture.
f2.8 has a very different depth of field on APS-C, 35mm or Medium Format.


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## Ysarex (Oct 22, 2014)

CameraClicker said:


> Ysarex said:
> 
> 
> > I compared *the same photograph* taken with two different cameras (sensor sizes). A comparison that would be interesting and meaningful to a photographer.
> ...



There does seem to be a lot of cross talk going on here. My concern is with this error stated in post #13: "I have full frame and APS-C bodies, and prime lenses, so I got out a tripod, a target and a tape measure. *Sensor size has no effect on DOF.*"

I posted a correction in post #43.



CameraClicker said:


> Frequently we make brief statements that are true in certain circumstances, but don't really illuminate sufficiently to permit the information to be used/understood in other situations.
> 
> Bokeh comes mostly from focal length, aperture, and distance to subject/distance to background.  If a smaller/larger sensor allows you to move with respect to your subject/background, that movement will be what affects the bokeh.  Put a 50 mm f/1.8 lens on a crop body, or on a full frame body, and you will be able to go and shoot with the same ISO, same shutter speed, and same aperture, and you will get an image with the same exposure, but different framing. If you want more bokeh, get a full frame body because for any given focal length, you can stand closer and still fit your subject in.



Moving the camera alters perspective and produces a different photograph -- not a valid comparison.



CameraClicker said:


> Get a medium format camera because the much larger sensor will let you stand even closer!  Standing closer is the part that will deliver more bokeh.  Same lens, same distance to subject, same aperture, same DOF, different framing if you have different sensor sizes.



Moving the camera alters perspective and produces a different photograph -- not a valid comparison.

Joe


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## theraven871 (Oct 22, 2014)

Ysarex said:


> CameraClicker said:
> 
> 
> > Ysarex said:
> ...



Joe, 
I agree with you.
If you take a 50mm 1.8 lens on a full frame vs crop sensor, you'll need to get CLOSER with the full frame to keep the same composition.
This, of course, will also affect your depth of field.   So its not an accurate test.


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## CameraClicker (Oct 22, 2014)

Ysarex said:


> CameraClicker said:
> 
> 
> > Ysarex said:
> ...


Joe, skip back to #35.  Bodies were changed to change sensors, lens, distance and all that were kept the same.  I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change.  There is no math involved, just a real world test.  In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected!  How is that a valid comparison.  Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.


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## Braineack (Oct 22, 2014)

CameraClicker said:


> Joe, skip back to #35.  Bodies were changed to change sensors, lens, distance and all that were kept the same.  I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change.  There is no math involved, just a real world test.  In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected!  How is that a valid comparison.  Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.



when you look, "A" has less DOF.

B and C appear to be the exact same image.

The test in #43 is not very good, the DOF area is already so large than any difference will be hard to measure/see.

The same test at f/2.8 with the 80mm/50mm of a stuffed animal, or something more 3D, filling the frame would be a better test.


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## Ysarex (Oct 22, 2014)

CameraClicker said:


> Joe, skip back to #35.  Bodies were changed to change sensors, lens, distance and all that were kept the same.  I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change.  There is no math involved, just a real world test.  In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected!  How is that a valid comparison.  Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.



You're not comparing apples to apples. If  the distance didn't change and the lens didn't change then you didn't take the same photo with the FF sensor camera or you cropped the FF camera image in which case I believe Wayne said something like are you joking?

.........f^2
H = -------
.........Nc

The math is simple and the math is clear. Unless you can demonstrate that changing "c" does not change "H" then *sensor size is a determinant factor in DOF.*

Joe


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## Derrel (Oct 22, 2014)

Goodness gracious, people....sensor size is a MAJOR factor in depth of field!! Do you want to be able to take pictures where objects from fairly close to Infinity are in good focus? Do you want to be able to shoot across a restaurant table AND also have the artwork on the back wall be recognizably in-focus? If the answer is yes, then shoot with a SMALL-sensor camera, like a digital Point & Shoot camera, or your cellphone camera.

Do you want to be able to shoot portraits in a garage studio or a living room studio, where you have only about five feet behind the subject's head to where you must hang your backdrop fabric or paper, and do you want the background to be noticeably OUT of focus? If the answer is yes, this is one of the ********primary*********, actual scenarios where I can almost always spot a DX or APS-C or m4/3 camera, as opposed to an FX sensor camera.

Do you want to shoot pictures of a person full-length, where the background just 20 feet behind them is pretty much unrecognizable? This is **exactly** what a 120 rollfilm camera and its 150mm short telephoto lens can do for you.

Do you want to shoot close-up artistic portraits where the eyes are in focus and the ears are wayyyyyyy out of focus, using flash, at f/5.6? Shoot on 4x5 sheet film. It has an amazing shallow depth of field character that smaller formats simply cannot match.


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## CameraClicker (Oct 22, 2014)

Braineack said:


> CameraClicker said:
> 
> 
> > Joe, skip back to #35.  Bodies were changed to change sensors, lens, distance and all that were kept the same.  I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change.  There is no math involved, just a real world test.  In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected!  How is that a valid comparison.  Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.
> ...



I had to go back and look at the original files.  I still don't see an obvious difference.  The target was about 8 feet from the camera, so if sensor size was a major factor, I would expect twice the sensor to make more of a difference.  Braineack and Theraven871 did successfully guess the correct file.

Here are the 3 files overlaid, with labels.


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## CameraClicker (Oct 22, 2014)

Ysarex said:


> CameraClicker said:
> 
> 
> > Joe, skip back to #35.  Bodies were changed to change sensors, lens, distance and all that were kept the same.  I don't see a difference in DOF between the 3 photos, so DOF didn't change (or didn't change a meaningful amount within my ability to focus on the target) with a sensor change.  There is no math involved, just a real world test.  In post 43 you had a full frame body with 80 mm lens selected and APS-C body with 50 mm lens selected!  How is that a valid comparison.  Remember, we are speaking of DOF caused by sensor, not caused by making a bunch of adjustments to try to get a similar result in a rectangle containing a compressed image.
> ...


Joe, you want to compare apples to apples, then you change focal lengths.  These are crummy photos but they should be about the same width.  I don't have an 80 mm prime lens so I used a ruler and a zoom.  EXIF data says 75 mm, but the ruler says they are about the same width.

  
................  FF ............................................................. APS-C ............................


So the image fills the frame about the same but I would not say the images are the same.  Look at what happens when you take 100% crops, the same size!

  
................  FF ............................................................. APS-C ............................

If you are printing portraits, your argument and math makes a degree of sense, but if you are doing other things, there are several moving parts to pay attention to.


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## Ysarex (Oct 22, 2014)

CameraClicker said:


> Braineack said:
> 
> 
> > CameraClicker said:
> ...




You're using the same lens from the same position on a FF and crop sensor camera -- you're cropping the FF sensor then and so this is a comparison of DOF between a crop sensor and a crop sensor -- you're proving that two crop sensors have the same DOF. Going to have to quote my niece again....

What you need to do is compare a FF sensor with a crop sensor *by taking the same photo with each.*

.........f^2
H = --------
.........Nc

You can't calculate DOF without the variable circle of confusion -- "c". "c" is a variable so it's value changes. The variable value of "c" changes with sensor size. Change sensor size and you change "c" in the above equation. Change "c" and you change "H". It can't get any clearer than that.

Joe


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## CameraClicker (Oct 22, 2014)

Joe, you may have to quote your niece again. LOL!

Let me run this by you.
Here are DOF calculator results for what I did:


 

So on the calculator it says "Use the actual focal length of the lens".  So I use some APS-C body to take a picture.  Then I use a full frame body, from the same place, same ISO, same aperture, same lens.  The calculator says APS-C should be total depth of 0.09 ft, or 1.08 inches.  It says the full frame should have more DOF, 0.14 ft, or 1.68 inches -- 56% more!

When I take those photos and look at the results,  , I don't see 56% more!  A couple of people here have said they see less, maybe, with full frame.

In my world, mathematical modeling is supposed to produce a result that you can get out a ruler and measure.  The experiment is not showing what the calculator seems to be predicting.


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## Braineack (Oct 22, 2014)

look at the foreground DOF.

The 4 is soft on the 5D but sharp on the crop bodies.

If I overlay the two images, and then match the black hash marks to the left of the numbers to each other and move the rows so the blur matches between the two, that lines up the 6 of the crop bodies to the 3 of the full-frame.

that looks to be about a half inch distance between the two.

here's a screen shot:


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## shefjr (Oct 22, 2014)

I don't know if anyone has seen this but, I thought it was a nice illustration kundalini did her on TPF. I haven't read all of the discussion so I'm posting this up after only reading the thread title.

So You Wanna See the Difference Between Full Frame and Cropped Sensors? | Photography Forum

I hope it is helpful. It really was for me.


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## CameraClicker (Oct 22, 2014)

Braineack said:


> look at the foreground DOF.
> 
> The 4 is soft on the 5D but sharp on the crop bodies.
> 
> ...


There's gotta be a better way to evaluate this!  I overlaid the files and masked out a strip so I can see the full frame on my left and APS-C on the right.  It looks like moving the crop file up one character so the FF '0' and crop foreground '1' align, then from front to back, they look even to me.  Probably time for new eyes, their warranty was up years ago.

You seem to be saying there may be a half inch less DOF in the full frame file?  The calculator says the full frame should be sharper for half an inch!


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## Braineack (Oct 22, 2014)

Oh wait all were shot at same spot and focal length and the full frame was cropped to match?


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## runnah (Oct 22, 2014)

I am getting a strong sense of déjà vu.


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## shefjr (Oct 22, 2014)

runnah said:


> I am getting a strong sense of déjà vu.


Does that mean that this thread is gonna "make my dick itch?" 
I went through the thread I recommended and see that Brianeack was involved in that thread trying to discuss this topic with WayneF.


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## runnah (Oct 22, 2014)

shefjr said:


> runnah said:
> 
> 
> > I am getting a strong sense of déjà vu.
> ...



I got a cream.


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## Derrel (Oct 22, 2014)

Cameraclicker: Are you aware that _depth of field in the close-up range is basically independent of lens focal length, and is instead dependent pretty much on MAGNIFICATION_ of the subject matter? Yes, it's true.

You mention how things ought to be able to be measured....but as I mentioned above in my reference to the Bob Atkins article on Depth of field, depth of field behavior can be categorized into three zones: 1)* the CLOSE-UP zone* 2)Intermediate distances and 3)Longer distances.

Again, as I mentioned earlier, depth of field behavior can be broken down into three different "types" of situations/shooting conditions. Your example of the three focusing targets demonstrate one of the anomalies that I mentioned above, some 70 posts back, that in the close-up range, DOF is dependent upon MAGNIFICATION of the subject, and lens focal length becomes basically....totally irrelevant. Weird, but true.

The reason your three-card focus chart shows basically the SAME depth of field is that it is a CLOSE-RANGE shot, and depth of field is caused because the three subjects have been reproduced at the same magnification.

Maybe look into the science of it. Here's what I mean.

*Close-up*
When the subject distance 
	

	
	
		
		

		
			





 approaches the lens focal length, the focal length no longer is negligible, and the approximate formulas above cannot be used without introducing significant error. At close distances, the hyperfocal distance has little applicability, and it usually is more convenient to express DOF in terms of magnification. The distance is small in comparison with the hyperfocal distance, so the simplified formula





can be used with good accuracy._ For a given magnification_,* DOF is independent of focal length*."

emphasis mine:_For a given magnification_,* DOF is independent of focal length*. Your shot of the three cards pretty much PROVES the theory, which you seem to have been unaware of...


from Depth of field - Wikipedia, the free encyclopedia

As you can see, Depth of Field is broken down under section 10 and 11 into sub-sections dealing with the different ways DOF behaves in close-up, moderate, and longer distance scenarios.


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## runnah (Oct 22, 2014)

I don't think we'll ever really know how this all works. It's a mystery, like dark matter, string theory and how planes fly.


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## Derrel (Oct 22, 2014)

The Online Photographer blog devoted about one week, several articles, and hundreds of comments and questions to exploring the different factors behind the science of depth of field. It's NOT that difficult to understand, but there are so many people spouting B.S. that it is difficult to know what is truth, partial truth, and utter B.S..

Like the way at reallllllly close distances, such as on close-up photos, the focal length no longer really affects DOF--but the magnification is what determines the DOF. That is why, on those three focus target cards, shot with different formats, with different lenses, from close range, but shown at the SAME degree of magnification, the DOF is independent of the focal length. The same behavior does NOT hold true once the distances grow longer.

Maybe we could think of it like a 500-pound bomb; if one goes off in a living room, the entire room is destroyed and EVERYBODY in there DIES...buuuut....75 yards away, NOT everybody dies, and the measurable performance of the bomb's blast changes significantly...and at a LONG distance, nothing is felt, just a little bit of noise is heard. Farther away still, only the smoke plume is seen. So: how do we characterize the explosion of a 500 pound bomb? Do we go with the close-up description? The intermediate? The long range? Or from, basically "Infinity"?

This thread started off with a simple question, but got filled up with different questions, misunderstandings, poor writing, replies that were messed up or misdirected, yadda yadda...we have people who have theory but no actual experience telling us they "KNOW" the science, yet seem to be really, actually, UN-aware of the science, to a pretty high level.


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## runnah (Oct 22, 2014)

i have yet to see a simple article/video describing how it all works. I have seen many that contradict each other. So honestly I have given up trying to fully understand the science behind it. I know how to use is practically and that is fine with me.


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## Overread (Oct 22, 2014)

The problem is much as Derrel points out - the physics behind it is solid and fixed; BUT a lot of people don't understand it - or only understand part of it. As a result when they teach others the second hand info is already incomplete. It then gets repeated out - mixed up - jumbled up and in the end we end up with a big mess of cross conflicting information. 

It's partly the result of the fact that most of us are users of photography, but not scientists understanding its full function). There are also some guidelines that sound like fact mixed in there too. 


Take Derrels' example of macro photography. Most macro shooters will understand it; however even within those circles people get confused. The background blurring on short focal length lenses is far less than on long - a 35mm can appear to have more depth of field than a 300mm macro lens on the same shot at the same magnification - because whilst the depth of field itself is the same the blurring of the background is far less distinct (esp if the shot has the subject grading into the background instead of a sharp drop of and then a longer distance to the background subject content).


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## CameraClicker (Oct 22, 2014)

Derrel said:


> Cameraclicker: Are you aware that _depth of field in the close-up range is basically independent of lens focal length, and is instead dependent pretty much on MAGNIFICATION_ of the subject matter? Yes, it's true.
> 
> You mention how things ought to be able to be measured....but as I mentioned above in my reference to the Bob Atkins article on Depth of field, depth of field behavior can be categorized into three zones: 1)* the CLOSE-UP zone* 2)Intermediate distances and 3)Longer distances.
> 
> ...


Last time I did this, I used a shorter lens and longer distance and got a similar result.  I didn't think the distance was all that close, and don't see a huge difference when looking at the whole files.  I thought shooting new files with a longer lens would be faster than looking for the old files and chose this lens because the 150 has it's own tripod mount.   I'm out of time again. I probably won't get back to it until next week.  Sounds like you recommend I do my own calculations using the formula instead of relying on the calculator.


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## photoguy99 (Oct 22, 2014)

****in magnets. How do they work?


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## shefjr (Oct 22, 2014)

"How exactly is a rainbow made? How exactly does the sunset? How exactly does the posi-trac rear end on a Plymouth work? It just does!"
Joe Dirts dad


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## Ysarex (Oct 22, 2014)

CameraClicker said:


> Joe, you may have to quote your niece again. LOL!
> 
> Let me run this by you.
> Here are DOF calculator results for what I did:
> ...



In the side by side DOF Master frames you're comparing two different photos taken with two different format cameras. In order to make a meaningful comparison you have to take *the same photo* with the two different cameras. In this example you need a 95mm lens on the 7D for the two photos to be the same. That will give you more DOF from the 7D and a hyperfocal distance of 550 feet instead of 870 feet -- as expected.

Joe


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## photoguy99 (Oct 22, 2014)

I just skimmed the thread but it doesn't look like anyone had pointed out that it's all a fool's game.

If you don't know how you're going to crop and what the final presentation size is and how far away viewers are going to be from the final photo, you can't calculate DOF as such. Also, Dof is a perceptual thing so even there one viewer is going to see it differently than another.

The online calculators can tell you what will most like be sharp enough, so you can tell if the model's ear and nose will both be sharp enough to count as in focus. Or if the tree and hill will be.

Generally.

If you print big, or if your audience is going to be nose to nose with the photo, you need to be more conservative still.

What they won't do is a good job of telling you what's not 'in focus'. Mostly we look at photos smaller than the conservative model assumes so there's more DOF than the model suggests. More stuff is sharp, in focus, than dofmaster said would be.

Open up for less DOF. Chimp to see if you got it. It's crude and dumb, but it's just about at effective as mucking about with calculators and formulae.


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## Ysarex (Oct 23, 2014)

photoguy99 said:


> I just skimmed the thread but it doesn't look like anyone had pointed out that it's all a fool's game.
> 
> If you don't know how you're going to crop and what the final presentation size is and how far away viewers are going to be from the final photo, you can't calculate DOF as such. Also, Dof is a perceptual thing so even there one viewer is going to see it differently than another.
> 
> ...



You did just skim. There were a lot of tangents and divergent sub posts but also one consistent question. There's a suggestion in post 11 and an assertion in post 13 that sensor size has no effect on DOF. In fact it does and it's taken a rather long time and some effort to get to the correct answer.

Complex as it may be DOF is a photographic phenomena that is understandable and definable and successfully manipulable within a reasonable working range. Just because it's complex doesn't mean we should relegate it to the province of fools.

Joe


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## photoguy99 (Oct 23, 2014)

Sure you can understand it and manipulate it. If you don't know your final print size when you're shooting, though, it's all wildly approximate.

Dofmaster and friends, with their answers out to 1/100th of a foot or whatever, yield a rather odd impression.

By the by, when I say it's a fool's game, I don't mean to call anyone a fool. It's an idiomatic phrase meaning roughly a pointless exercise.


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## Ysarex (Oct 23, 2014)

photoguy99 said:


> Sure you can understand it and manipulate it. If you don't know your final print size when you're shooting, though, it's all wildly approximate.



No. It is slightly approximate and so works well. For example it's empirically established that people will view a print at an average distance relative to the size of the print. For example when's the last time you viewed a highway billboard from a distance of 6 feet? And even if you did we could discount you as anomaly. Averages have been calculated and they apply.

Yes there's no need for three digit precision in the calculators, but the math behind the calculations is well tested and functional.

Joe



photoguy99 said:


> Dofmaster and friends, with their answers out to 1/100th of a foot or whatever, yield a rather odd impression.
> 
> By the by, when I say it's a fool's game, I don't mean to call anyone a fool. It's an idiomatic phrase meaning roughly a pointless exercise.


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## photoguy99 (Oct 23, 2014)

I sit a pretty constant distance from my computer screen. Guess where I look at almost all photos?

I think you place excessive faith in these things, but I am ok with just leaving it as a disagreement.

ETA: the various calculators and formulae do indeed work well to ensure that stuff we want to be in focus is in fact sufficiently sharp. Because they are fairly conservative. What they are less useful for, and largely nobody cares, is telling us what's out of focus 

They don't really tell us DOF. They give us a moderately strong and useful lower bound.


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## Braineack (Oct 23, 2014)

shefjr said:


> "How exactly is a rainbow made? How exactly does the sunset? How exactly does the posi-trac rear end on a Plymouth work? It just does!"
> Joe Dirts dad


how do you even?


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## shefjr (Oct 23, 2014)

Braineack said:


> shefjr said:
> 
> 
> > "How exactly is a rainbow made? How exactly does the sunset? How exactly does the posi-trac rear end on a Plymouth work? It just does!"
> ...


Did I get the quote wrong? 
I was just trying to add a little levity to an otherwise at times contentious thread and thought it was a fitting response to the "how do magnets work?"


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## Vince.1551 (Oct 23, 2014)

I think it's about time we start a TPF University [emoji23]


Sent from my iPhone using Tapatalk


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## Braineack (Oct 23, 2014)

shefjr said:


> Did I get the quote wrong?
> I was just trying to add a little levity to an otherwise at times contentious thread and thought it was a fitting response to the "how do magnets work?"



no, I was asking, how do you even?

saying "I can't even" is very popular amongst us cool kids today


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## shefjr (Oct 23, 2014)

Braineack said:


> shefjr said:
> 
> 
> > Did I get the quote wrong?
> ...


Damn it! I'm not cool anymore! When did that happen? Maybe I never was. Noooooo!


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## astroNikon (Oct 23, 2014)

geez .. I ran out of popcorn .. had to get more


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## Ysarex (Oct 23, 2014)

photoguy99 said:


> I sit a pretty constant distance from my computer screen. Guess where I look at almost all photos?



And guess who brought up final print size as an issue? So then it's not a big issue and you were just blowing smoke.



photoguy99 said:


> I think you place excessive faith in these things, but I am ok with just leaving it as a disagreement.



"Excessive faith?" Hmmm, 40 years a full-time photographer and 100s of thousands of photos later and I thought I was seeing consistent science. I'm going to be OK continuing to think that.

I don't carry around a calculator when I take photos and wouldn't suggest it as useful practice, but I do understand how DOF functions and I make decisions when taking photos of how I intend DOF to render in a photo. By understanding it and having previously worked through the math I make more effective decisions with predictable outcomes. The calculators and the math are useful in helping us understand -- informed practice then leads to more effective manipulation. *That's what the calculators are for.* We don't dismiss using them and dismiss refining our understanding as a fools game because they're ungainly in the field or only approximate in application.  

Got to admit those first 100 thousand photos I was still on shaky ground, but since then I'm in the grove. 

Took this photo earlier this summer. I consciously controlled the DOF when I took the photo and I got the results I expected. I know what people are seeing as in and out of focus in this photo and I planed that before I clicked the shutter. I didn't use a calculator in the field. I did all the math in advance over the past 40 years and informed my practice so that now I can produce predictable results.

Joe










photoguy99 said:


> ETA: the various calculators and formulae do indeed work well to ensure that stuff we want to be in focus is in fact sufficiently sharp. Because they are fairly conservative. What they are less useful for, and largely nobody cares, is telling us what's out of focus
> 
> They don't really tell us DOF. They give us a moderately strong and useful lower bound.


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## photoguy99 (Oct 23, 2014)

Goodness. What a lot of photos you have taken. You must be the greatest.

Your snotty remark about who brought up final print shows that you're not paying attention to what I'm saying. In this modern world the 'final print size' isn't even fixed. Since we mainly look at photos on monitors of various sizes shapes and pitches and at various viewing distances, DOF is more variable than ever.


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## Ysarex (Oct 23, 2014)

photoguy99 said:


> Goodness. What a lot of photos you have taken. You must be the greatest.
> 
> Your snotty remark about who brought up final print shows that you're not paying attention to what I'm saying. In this modern world the 'final print size' isn't even fixed. Since we mainly look at photos on monitors of various sizes shapes and pitches and at various viewing distances, DOF is more variable than ever.



Not clear enough there; I didn't take them all personally, but I was responsible for evaluating them all and instructing on their production in detail including DOF rendition so I have a legitimate claim of directorial participation and the number is accurate.

And I think my snotty remark indicates I'm paying very good attention.

Joe


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## photoguy99 (Oct 23, 2014)

Let the record show that I tried to be polite here. I really did.


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