# Why Should We Care About Crop Factor?



## deveaushawn (Dec 29, 2013)

I'm new to dSLR photography. I've had plenty of Point-n-Shoot cameras over the years, but have only recently jumped into and started to learn about the finer points of the dSLR realm.

I went with a MFT system (E-M5) because the IQ is great and the system is relatively light and compact. One of the first things I began reading/hearing about is Crop Factor. I've done a great deal of research and have yet to understand why anybody gives two hoots about it.

As I understand it, what we call Full Frame is in fact just a crop of the old 8x10 format, but you don't hear anybody talking about a 35mm lens being equivalent to 170mm on 8x10. (I'm totally making those numbers up!)

Truth be told, I actually find the whole thing rather confusing. The only information I've seen that offers an explanation about the significance of Crop Factor is that it gives Full Frame shooters a reference point to compare what Field of View will look like, but for those of us who aren't familiar with the 35mm FoV, why would we care?

Am I missing the point?

Thanks,

Shawn


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## ShootRaw (Dec 29, 2013)

Because in tight spots certain focal lengths can not work due to the crop factor..Can be annoying sometimes not having the room to compose correctly..On the flip side,dx being cropped uses the most center part of the pic which is normally the sharpest..


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## amolitor (Dec 29, 2013)

Yes, I find the whole 'X is equivalent to Y' nonsense confusing and not very useful.

There was a time when it made sense, when they were building 35mm film cameras, and crop-sensor DSLRs, simultaneously. They did, at that time, need to emphasize to 35mm film shooters that while their existing lenses WOULD work on the new digital bodies, there was gonna be a difference in field of view. That was a very specific marketing tactic for a very specific interval in the industry.

It's no longer relevant, and it creates far more total confusion than clarification now.


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## Ysarex (Dec 29, 2013)

Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.

Joe


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## Judobreaker (Dec 30, 2013)

Ysarex said:


> Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.
> 
> Joe




Not really...
DOF has nothing to do with the size of the sensor. The only reason people think it does is because you'd need to get closer to the subject with a full frame sensor to fill the frame. It's the different subject distance that changes the DOF, not the actual size of the sensor.


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## DanielLewis76 (Dec 30, 2013)

I am no expert and new to photography but whilst the whole 1.6 thing seems relevant to mm length between the two for the same lens I just assumed the main reason to go FF rather than cropped is that if they are both, for example, 16mp as the sensor is bigger the pixels are bigger which gives better quality pictures and better low light functionality.


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## JTPhotography (Dec 30, 2013)

The only true difference between crop and full frame is that FF produces a much higher quality image.

The differences that people seem to focus on relate to lenses. Use DX lenses on a DX body and the only difference is what I stated above. If you only intend to shoot DX and you have only DX lenses, the entire concept becomes moot. Use FX lenses on a DX body and the photo gets cropped, simple as that. DX specific lenses are designed to project the image onto a smaller area and will vignette if you use them on a FF body.  The concept is ONLY relevant to people who shoot DX and intend to use FF lenses.

As stated above, DOF is ONLY an issue when you are using FX and DX lens on DX format. You have to move yourself in relation to the subject to match focal lengths.


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## Solarflare (Dec 30, 2013)

If you want to communicate with others, you should agree on some kind of, well, communication protocol. Its really trivial for four third sensors: just multiply by 2 and you're at the equivalent for fullframe.

And FYI, small format isnt the crop of anything, but was two frames of movie film. It was developed to have a camera that fits into your hands nicely.

While the only reason Four Third was developed was because back then, it was the largest size for digital sensors they could create reasonably cheaply.


Also, I do believe that small format will stay on the long term. Thats because cameras like the new full frame Sony A7 arent any larger than Micro Four Thirds, in fact its SMALLER than some of them. And making cameras smaller than that isnt very practical, simply because then they wouldnt fit well into human hands anymore.

Another reason is that with even smaller sensors than the full small format, its getting hard to get shallow depth of field, a popular creative element for photography.

Full frame is already VERY small. Its just 36x24mm. Thats like a bit more than the nail of my own thumb. And sensors are getting cheaper over time, too.

Right now, the best cost/performance deal is APS-C. The sensors for it are still no important factor for any reasonable cameras, and the performance is pretty close to full frame. But full frame is getting cheaper and more available, too, and in the long term, I think it might regain the position it had in the film days.

Dont get me wrong. The masses will always use small sensors. But people who care for image quality will use large sensors for their better quality and the creative possibilities of shallow depth of field.



I certainly agree though that Micro Four Thirds is a great system. Thats because its an actual open standard and any company can participate. However, as a sensor size it makes little sense, because you dont actually save that much in respect to size and cost and get an inferior performance. The only case when MFT really gets the advantage is if you want to have extreme focal lengths, such as for bird photography; then you certainly have to carry a LOT less around. You will need good light though.





Judobreaker said:


> DOF has nothing to do with the size of the sensor. The only reason people think it does is because you'd need to get closer to the subject with a full frame sensor to fill the frame. It's the different subject distance that changes the DOF, not the actual size of the sensor.


 Well, you're wrong about that.

DOF depends upon 4 variables:
- Focal length
- Distance to subject
- Current Aperture
- Sensor resolution (or resolution of your print)

And what exactly focal length means depends upon sensor size. Thus DOF depends upon sensor size.






JTPhotography said:


> The only true difference between crop and full frame is that FF produces a much higher quality image.


 Not THAT much higher, actually. Especially since there are a lot of excellent prime lenses for MFT around. And with the newest Olympus OM-D, one can use these old FT zooms too, and there are apparently very high quality zooms from Olympus around which are quite affordable now, since FT has died as a format.

The sensor though is inferior. But not THAT much.


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## sleist (Dec 30, 2013)

deveaushawn said:


> Truth be told, I actually find the whole thing rather confusing. The only information I've seen that offers an explanation about the significance of Crop Factor is that it gives Full Frame shooters a reference point to compare what Field of View will look like, but for those of us who aren't familiar with the 35mm FoV, why would we care?
> 
> Am I missing the point?
> 
> ...



As long as there are lenses that can be used on cameras with different sized sensors (i.e. FX/DX), there will be a need for people to know the resulting image from that lens will be different depending on camera sensor size.  Saying that a 50mm lens on a crop body is the same as a 75mm lens in a FX body is (in my opinion) simply meant to be an approximation in an effort to set expectations for consumers.  It's also easier to help people moving to a different format such as m43 to know that a 45mm lens approximates the image one might get in a 85mm lens on FX body.  Too many people take these approximations to be more exact than they were ever intended and this is where the trouble starts.

To your point, if you only have an m43 body and never used film or FX sensors then these comparisons mean less to you than other people.  However, living in a vacuum is not always helpful - particularly when so much photography took place before digital and sensors ever existed.  If you pick up photography texts to learn a technique, or want to emulate a certain photographer or photographic style, these approximations may be very helpful for you.


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## deveaushawn (Dec 30, 2013)

sleist said:


> To your point, if you only have an m43 body and never used film or FX sensors then these comparisons mean less to you than other people.  However, living in a vacuum is not always helpful - particularly when so much photography took place before digital and sensors ever existed.  If you pick up photography texts to learn a technique, or want to emulate a certain photographer or photographic style, these approximations may be very helpful for you.



That's exactly the reason I asked the question, sleist. I'm trying to understand what is meant by a 'normal' or 'standard' Full Frame lens e.g., the 50mm. Do I buy a 25mm m43 lens or a 50mm m43 lens? Or a 25mm FF lens with an adapter? Or can I use a DX lens (not sure what focal length, but you get the idea)?

It all seems quite confusing to a n00b like me! 

The easy solution is to stick with m43 lenses, but I have a bunch of Nikon glass I want to play with, and it will help if I understand how the 2x crop is affecting my shots.

Thanks,

Shawn


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## Steve5D (Dec 30, 2013)

It's simple: The bottom line is that you should find what works for you, and use that...


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## underemployed (Dec 30, 2013)

deveaushawn said:


> I'm new to dSLR photography. I've had plenty of Point-n-Shoot cameras over the years, but have only recently jumped into and started to learn about the finer points of the dSLR realm.
> 
> I went with a MFT system (E-M5) because the IQ is great and the system is relatively light and compact. One of the first things I began reading/hearing about is Crop Factor. I've done a great deal of research and have yet to understand why anybody gives two hoots about it.
> 
> ...



Have you ever taken any pictures with a full frame camera?


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## deveaushawn (Dec 30, 2013)

@ underemployed: 
No.


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## timor (Dec 30, 2013)

Ysarex said:


> Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.
> 
> Joe


Joe, now I am confused even more. How the size of the medium alone is responsible for DoF. I thought *only* lens (and maybe tilt and swing of it) is responsible for DoF,  not the size of the negative. Or sensor for that matter. Size of the negative cannot change the size of COC with given lens. Or I am wrong on this one ?


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## timor (Dec 30, 2013)

deveaushawn said:


> @ underemployed:
> No.


That's OK man, as long, as you don't touch lenses designed for different format cameras, you will be OK (not confused) with this whole "crop factor" business.

When comes to "talking about a 35mm lens being equivalent to 170mm on 8x10" you don't hear it as you are not involved in this kind of photography. Maybe from the educational PoV you should read "The Camera" or "Camera And Lens" by A. Adams, that will explain a lot.

I am not sure, if 8x10 is a "full frame", there are bigger cameras.


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## KmH (Dec 30, 2013)

timor said:


> Ysarex said:
> 
> 
> > Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.
> ...


Judobreaker explained it. The point of focus distance changes when you use a crop sensor to accommodate the apparently cropped FoV sensor delivers.

Point of focus distance affects DoF.


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## sleist (Dec 30, 2013)

> Joe, now I am confused even more. How the size of the medium alone is responsible for DoF.



What I think he means to say is that the sensor size impacts the depth of field capabilities of a given lens.  It is not only factor though.
The smaller the sensor, the larger the minimum possible depth of field will be regardless of the lens used.  A 50mm f/1.4 lens at f1.4 will have a smaller depth of field on a large sensor than the same 50mm f/1.4 at f1.4 on a smaller sensor.  Even if you used a 35mm f/1.4 on the DX or a 24mm f/1.4 on m43 in order to better approximate a similar field of view, you would still have a larger minimum DOF on a smaller sensor.

Ultimately, what Steve5D states is the truth - find what works for you and use it.


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## timor (Dec 30, 2013)

KmH said:


> timor said:
> 
> 
> > Ysarex said:
> ...


Please, give me the link. I don't understand how the distance from the subject changes, when using crop sensor.


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## timor (Dec 30, 2013)

sleist said:


> What I think he means to say is that the sensor size impacts the depth of field capabilities of a given lens.  It is not only factor though.
> The smaller the sensor, the larger the minimum possible depth of field will be regardless of the lens used.  A 50mm f/1.4 lens at f1.4 will have a smaller depth of field on a large sensor than the same 50mm f/1.4 at f1.4 on a smaller sensor.  Even if you used a 35mm f/1.4 on the DX or a 24mm f/1.4 on m43 in order to better approximate a similar field of view, you would still have a larger minimum DOF on a smaller sensor.


Thank you Sleist, that's the mystery I have to understand, how given lens is starting to create smaller CoC, when the size of the sensor or negative is smaller.


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## JTPhotography (Dec 30, 2013)

I think this issue is getting overly confused.

If I set up a tripod and take a photo with a crop sensor camera and 50mm lens, then, keeping the tripod in place and using the same settings, swap the crop body with a full frame body and take the same exact photo, the ONLY difference in the two photos is that there would be less stuff showing around the edge of the photo taken with the crop body. DOF is the same, distortion is the same, the lens is projecting the same image onto the two sensors. If you take the FF body and move the camera and tripod closer and try to recreate the exact image taken on the crop body, your DOF would change because you have moved the camera in relation to the objects in the photo. Make sense?


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## Derrel (Dec 30, 2013)

There **is a significant, noticeable and a very, real difference** between shooting with an APS-C or other smaller-sensor digital camera, and a 35mm-sized or 24mm x 36mm sensor camera( called FX by Nikon, or FF, AKA full-frame digital by many) as well as between a 35mm sensor size camera, and a medium-format rollfilm type camera, like say a 6x6 square camera like a Hasselblad. Mamiya, or Rollei,etc..

The simplest explanation is that the smaller the sensor or film size, the MORE depth of field there is at each picture "angle". Let's say we want to make a normal-lens picture--not an ultra-telephoto, tightly frames image, and not an ultra wide-angle panoramic image, just a normal picture. A point and shoot with a teeny-tiny sensor has almost infinite depth of field with its normal lens; an 8x10 view camera has very little depth of field with its normal lens; in between those extremes, there is MORE depth of field at each picture angle of view, as the sensor or film size gets smaller.

Here is one of the best articles I've seen on the issue. One that's accurate, and factual, unlike many pieces written about this issue.
Depth of Field and the Small-Sensor Digital Cameras - photo.net

SOME BULLET POINTS:



For an *equivalent field of view*, the small-sensor camera has at least 1.6x *MORE*depth of field than a full-frame camera would have - when the focus distance is significantly less then the hyperfocal distance (but the full-frame format need a lens with 1.6x the focal length to give the same view).
Using the *same* lens on a small-sensor camera and a full-frame camera, the small-sensor image has 1.6x *LESS* depth of field than the full-frame image would have (but they would be different images since the field of view would be different)
If you use the *same* lens on a small-sensor camera and a full-frame camera and *crop* the full-frame image to give the same view as the digital image, the depth of field is *IDENTICAL*
If you use the *same* lens on a small-sensor camera and a full-frame camera, then shoot from *different distances* so that the *view is the same*, the small-sensor image will have 1.6x *MORE* DOF then the film image.
Close to the *hyperfocal distance*, the small-sensor camera has a *much more* than 1.6x the DOF of a full-frame camera. The hyperfocal distance of the small-sensor camera is 1.6x less than that of a full-frame camera.


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## amolitor (Dec 30, 2013)

The whole thing is made immensely complex by the fact that nobody ever does a good job of explaining what they're holding fixed and what they're changing.

Some examples:

- in order to frame the same subject using the same lens, you have to step back when using the crop sensor, do the distance to subject is different
- in order to frame the same subject from the same shooting position, you have to use an "equivalent length" (ugh!) lens, which is shorter when you're using a crop sensor, which means (among other things) that at the same aperture (f-number) the physical size of the hole is smaller


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## timor (Dec 30, 2013)

amolitor said:


> The whole thing is made immensely complex by the fact that nobody ever does a good job of explaining what they're holding fixed and what they're changing.
> 
> Some examples:
> 
> ...


OK, so CoC of one lens doesn't change on smaller sensor, so they are giving the same DoF. Unless we want the same angle of view, and for that we use shorter lens on smaller sensor, which automatically makes the aperture smaller, which gives smaller CoC, which makes the DoF deeper. Question: if we print the same size picture taken with FF and 50mm at let say f8 and picture taken with cropped sensor with "equivalent lens" and same aperture, what's gonna happen to DoF in this prints ?


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## astroNikon (Dec 30, 2013)

timor said:


> Please, give me the link. I don't understand how the distance from the subject changes, when using crop sensor.




http://www.thephotoforum.com/forum/photography-beginners-forum/212708-so-you-wanna-see-difference-between-full-frame-cropped-sensors.html


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## timor (Dec 30, 2013)

Another question: is a flange distance important for DoF ?


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## vintagesnaps (Dec 30, 2013)

To me it's similar to being out taking pictures and going from using a 135mm to a 50mm; obviously the field of vision is different and what I'm recording is different. When I've been out using my digital camera which has a crop factor and one of my film cameras, I could use the same length lens and I'm not going to get the same field of view, I'm seeing something different and would have to change my vantage point if I want to get a comparable photo with both.

I've never compared flange difference in photos using different cameras that I have, probably because I haven't been out using two different SLRs at the same time; I usually take along maybe a rangefinder w/a 45mm lens and an SLR w/a 135mm, or my digital camera and a film rangefinder using the same lens where the crop factor makes a difference anyway.


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## Ysarex (Dec 30, 2013)

Judobreaker said:


> Ysarex said:
> 
> 
> > Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.
> ...



No.

I did give a very brief answer and I see I was away far too long.

Assumption:  You want to take the exact same photo with two different cameras that  have different size sensors. In order to take the exact same photo you  will have to be at the exact same camera/subject distance. For the  framing to be exactly the same you'll need to use lens focal lengths  that produce the same angle of view/over sensor size. Let's pick two  cameras: A Canon 5D and my little Samsung portable. In order to achieve  the exact same cropping and perspective between the two cameras they  must be used from the same camera position -- let's do 10 feet. To get  the same framing as a 50mm lens on the 5D I'll need a 10.8mm lens on my Samsung. NOTE: In terms of content this is the same photo. The framing is the same and the perspective is the same. Andrew's right -- you got to explain what's being held constant. For this comparison it only makes sense that you're using the different cameras to take the same photo content/perspective.

I want to use the same ISO with each camera and so I will get the same shutter speed f/stop combinations for both to get a good exposure. Let's assume the f/stop then is f/8.

The 5D will give me a total DOF of 6.28 feet with the near limit at 7.8 feet and the far limit at 14 feet. My Samsung's DOF will reach to infinity with the near limit at 4 feet. There is nothing you could do with my Samsung camera to force it to give you less DOF while taking the same photo except to open up the lens aperture. If you open the lens aperture on the 5D the same amount you will be forced to always have less DOF from the 5D. You CAN NOT make the two cameras produce the same DOF taking the same photo unless you shot the 5D at f/11 and my Samsung at f/2.

Now it's not that DOF is a function of sensor size directly. It's an indirect effect but no less real. *It's this: In simplest form DOF = f/stop + magnification.* When you do the math on magnification and factor in that you're using the cameras to take the exact same photo, you must get more DOF from smaller sensor cameras and less DOF from larger sensor cameras.

Joe


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## Ysarex (Dec 30, 2013)

timor said:


> Another question: is a flange distance important for DoF ?



Nope.


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## Ysarex (Dec 30, 2013)

timor said:


> amolitor said:
> 
> 
> > The whole thing is made immensely complex by the fact that nobody ever does a good job of explaining what they're holding fixed and what they're changing.
> ...



We don't assign CoC values to lenses. CoC values used to calculate DOF are assigned based on the size of the recording media: film/sensor. So for a 35mm film or digital FF camera a CoC value around .025mm is common. My little Samsung portable that I noted above with a 1/1.7" sensor would have a CoC value around .007mm. Going the other way a 4x5 sheet film camera would get a CoC value of .1mm and that's one of those "I can't quite put my finger on it" differences that's very real between photos taken with modern digital cameras versus photos in the middle of the last century taken with larger cameras. The history of photography is the history of shrinking media and the progressive increase in DOF in everybody's photos.

And great question about what happens when you make a print. To really deal with DOF you need to bring the enlargement size to print into the equation. If you're standardizing on say an 8x10 inch print then the smaller media has to be enlarged more and as a result tighter constraints need to be placed on the CoC value. That's why we assign CoC values to media size -- it's part of the equation.

Joe


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## timor (Dec 30, 2013)

Aha. Thanks. I always though, that CoC is an optical function of the lens and actually describe the ability of the lens to create the largest blur spot indistinguishable from a point. What you said means, that a LF lens, when directed on small, 1/1.7'' will produce 0.07mm spot, when directed on FF sensor will produced 0.25mm spot, when directed on 4x5 negative will become lazy and the spot will be of 0.1 mm. So, what will be the spot on other materials like ground glass or photographic paper ? And why optical properties of the lens should change with the recording media ? 
I don't think, that we assign CoC values to the media. We assign the maximum *acceptable *value of CoC to the media, which in turn is the minimum quality requirement for the lens for that medium. Your tiny sensor wouldn't yield any usable image, if shot with LF lens.


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## amolitor (Dec 30, 2013)

Interestingly, if we assume that we're making the same size prints from both, CoC becomes smaller for crop sensors. You're enlarging more, so you must have a higher standard for "what's sharp" at the sensor. This causes the crop sensor to have somewhat less DoF. Other factors, however, dominate, and taken all together we generally consider the crop sensor to have, in general terms, more depth of field.

In general, cropping may be considered to reduce depth of field, and a crop sensor is, as has been noted, in essential ways precisely the same as shooting with a larger sensor, and then cropping the result.


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## Ysarex (Dec 30, 2013)

amolitor said:


> Interestingly, if we assume that we're making the same size prints from both, CoC becomes smaller for crop sensors. You're enlarging more, so you must have a higher standard for "what's sharp" at the sensor. This causes the crop sensor to have somewhat less DoF. Other factors, however, dominate, and taken all together we generally consider the crop sensor to have, in general terms, more depth of field.
> 
> In general, cropping may be considered to reduce depth of field, and a crop sensor is, as has been noted, in essential ways precisely the same as shooting with a larger sensor, and then cropping the result.



Yes. That can sound like it's backwards but the reduction in magnification when the photo is taken is the dominant factor. That's a factor enforced in practice by the requirement to use shorter focal length lenses. You ask the question what's a normal lens focal length and a 35mm film user is going to say 50mm. Now folks using an APS-C sensor think of a 50mm lens as a portrait length lens. When I shot 6x7 I had a 58mm Grandagon that was a super wide angle. When I shot 4x5 sheet my normal lens was 150mm and a 65mm lens was super-wide.

To use the smaller media we have to reduce the lens focal length to capture the same content. Putting the whole package together including making an enlargement we develop "standard" CoC values that we attach to the media size. It really does boil down to DOF = f/stop + magnification. Magnification here is tricky because it's a complex combination of magnification calculated as focal length and subject distance as well as magnification to enlarge the image to print.

Think of it this way: Again assume a standard scene -- this time a landscape with an horizon at infinity. Maximum DOF advantage will occur with the lens set at the hyperfocal distance for the f/stop used. To maintain the exact same content in the photo each reduction of the media size will require a shorter lens focal length and at the same f/stop the hyperfocal distance will keep moving closer to the camera. Hyperfocal distance is calculated based only on lens focal length, f/stop and CoC. The media size is a factor because it forces the use of a different lens focal length to maintain the same content. The result again is more DOF in practice using the smaller media. Again using the 5D and my Samsung as an example the hyperfocal distance for the 5D with a 50mm lens at f/8 is about 34 feet. For my Samsung with a 10.8mm lens at f/8 it's 1 and 1/2 feet.

Now think of it this way: I used to use an Arca view camera that was multi-format. I had a 4x5 back for the camera as well as 6x7 roll backs and even an adapter that would let me attach my Nikon camera body. Put a 75mm Super Angulon on that camera with the 4x5 back and you have a super-wide camera. With the lens set to f/11 and the subject at 17 feet you have DOF that reaches infinity. Hyperfocal distance for that lens at f/11 is 16 and 1/2 feet. Don't move the camera. Don't even re-focus the camera. Let's just swap off the 4x5 back for the 6x7 back. That 75mm lens is now a normal lens and the DOF no longer reaches infinity. It's the same lens. We haven't even touched it but now at f/11 there's only 40 feet of DOF when just a moment ago there was DOF reaching infinity. Next we'll again swap backs without so much as touching the lens. This time let's mount my Nikon F2 body. That 75mm is now a portrait lens and set to f/11 there's only 13 feet of DOF when a moment ago there was 40. Through this back swapping we haven't so much as touched the lens. The camera has remained stationary and not moved a mm. We're cropping the photo differently with the backs, but why should the DOF change at all? The lens hasn't been changed. Then lens hasn't been moved. The f/stop hasn't been moved. And the reason is because we're changing the CoC value with the size changes in recording media.

Now this last example makes you think it's the 4x5 that's got all the DOF and the 35mm is the one with less DOF. But in practice what we're really going to do is take the same photo with both cameras and to get approx. the same angle of view on the Nikon that the 75mm gives on the 4x5 we're going to mount a 24mm lens on the Nikon. On my little Samsung that's going to be a 6mm lens.

Joe


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## timor (Dec 30, 2013)

That would be interesting experiment, but it won't work this way. DoF really is for the print, not a negative. All three negatives will have same CoC, now enlarge them to 16x20. Off course smaller negs gonna loose DoF much faster. In print from 4x5 CoC on the print will be enlarged only 4 times, from 35mm over 11 times. Forget sharpness with that.

Well, with DoF in the print one has to take in account the viewing distance to. I hope standards are set in such a way, that DoF, let say in 11x14 print, will look from FF and cropped sensor very similar.


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## Ysarex (Dec 30, 2013)

timor said:


> Well, with DoF in the print one has to take in account the viewing distance to. I hope standards are set in such a way, that DoF, let say in 11x14 print, will look from FF and cropped sensor very similar.



Of course you can't control how someone is going to look at a print. Some artists, when work is hung in a gallery will place a rope not only to keep folks from touching the work but also to help place them at a distance from which the artist wants them to view the print. The only study that I'm familiar with is one conducted using different size photos hung on gallery walls where the viewer's voluntary position was recorded. What they discovered is that within a standard range of 5x7 through 20x24 prints people on average would stand back a distance to view the photo that about equaled double the long side of the photo. If that's correct then we'd assume most people would comfortably stand back about 30 inches to view an 11x14 print.

Who gets together however in some kind of a standards organization meeting and decides for all of us what CoC values should be used by the industry is a mystery to me. I remember when I was first jarred into thinking about this was back in the late 70s when I discovered that the CoC value published by Nikon for Nikon DOF lens scales was different than the CoC value published by Leica. It was one of those WTF moments for me. I had to figure the Germans knew what they were doing and, especially since the Nikon value was more lax, those Japanese marketing bleeps were probably resting their thumbs on the scale to make it look like their lenses yielded more DOF than they really did. Now I know that wasn't the case; the Germans were just making bigger prints. 

Kidding aside you could contact Don Fleming at DOF Master and ask him for authoritative references. Be interesting to know where he sourced his figures. I know he uses that Leica value for 35mm instead of the sloppy Nikon one.

Joe


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## DiskoJoe (Dec 30, 2013)

deveaushawn said:


> I'm new to dSLR photography. I've had plenty of Point-n-Shoot cameras over the years, but have only recently jumped into and started to learn about the finer points of the dSLR realm.
> 
> I went with a MFT system (E-M5) because the IQ is great and the system is relatively light and compact. One of the first things I began reading/hearing about is Crop Factor. I've done a great deal of research and have yet to understand why anybody gives two hoots about it.
> 
> ...



Crop factor is important for DOF and also for distance that would need to be used for lighting. There is a lot of geometry that is involved with lighting and bouncing flash and the equivalent distance in an important factor to hitting the target properly.


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## Ysarex (Dec 30, 2013)

timor said:


> That would be interesting experiment, but it won't work this way. DoF really is for the print, not a negative. All three negatives will have same CoC, now enlarge them to 16x20. Off course smaller negs gonna loose DoF much faster. In print from 4x5 CoC on the print will be enlarged only 4 times, from 35mm over 11 times. Forget sharpness with that.



Number theory is just that -- theory. This only makes sense in practice. It's just like the algebra that you can use to calculate DOF limits. The math will always yield a number for the far limit, but at some point we just look at that number and say -- yo, that's infinity. So the whole has to be processed as a whole. Go to DOFMaster and look at Don's CoC table: Circles of Confusion for Digital Cameras Those values are all tied to sensor size because the CoC value is about the whole in practice. Run some simulations with the DOFMaster online calculator. The CoC value displays in the window and the only way you can get it to change is to alter the format/sensor size. He's got it right.

Joe


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## timor (Dec 30, 2013)

I tried, but cannot run the simulation let say for 6x7 on lenses for large format. :meh:


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## imagemaker46 (Dec 31, 2013)

Crop factor is great when you are using a long lens and could use a little more.  Crop factor sucks when you are using a wide angle and could use a little less.


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## Steve5D (Dec 31, 2013)

imagemaker46 said:


> Crop factor is great when you are using a long lens and could use a little more.  Crop factor sucks when you are using a wide angle and could use a little less.



That's probably the best description I've ever read!


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## Judobreaker (Dec 31, 2013)

Solarflare said:


> Judobreaker said:
> 
> 
> > DOF has nothing to do with the size of the sensor. The only reason people think it does is because you'd need to get closer to the subject with a full frame sensor to fill the frame. It's the different subject distance that changes the DOF, not the actual size of the sensor.
> ...




Wait... what? You're saying the focal length of my lens changes if I remove it from my D800 and place it on my D7000? That's interesting... 

The focal length of a lens is always the same (unless it's a zoom lens, but then it is always the same range). The only thing changing with a different sensor size is the field of view, the physics don't magically change.
The only reason that the DOF varies is because people generally tend to get closer to the subject when they are using a larger sensor.





imagemaker46 said:


> Crop factor is great when you are using a long lens and could use a little more. Crop factor sucks when you are using a wide angle and could use a little less.



My D800 has a more or less similar pixel density on its sensor as my D7000. This means that if I crop my D800 image in Photoshop with the same factor as a crop sensor I get more or less the same image. It's not the fact that the sensor is smaller that you can zoom in more, it's the pixel density that does the trick. Given the same density, the size of the sensor doesn't matter at all.


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## Derrel (Dec 31, 2013)

Ysarex said:
			
		

> >post 32>>>Think of it this way: Again assume *a standard scene* -- this time a landscape with an horizon at infinity. Maximum DOF advantage will occur with the lens set at the hyperfocal distance for the f/stop used. To maintain the exact same content in the photo each reduction of the media size will require a shorter lens focal length and at the same f/stop the hyperfocal distance will keep moving closer to the camera. Hyperfocal distance is calculated based only on lens focal length, f/stop and CoC. The media size is a factor because it forces the use of a different lens focal length to maintain the same content. The result again is more DOF in practice using the smaller media.> SNIP>
> Joe



See, the process Joe described above was EXACTLY the reason Kodak invented the tiny "disc format" snapshot/purse/carefree film camera format back in the 1970's. Yes, Kodak invented a whole NEW format size as a way to get unlimited depth of field pictures for snapshooters! Using bigger film formats, like 126 cartridge, the minimum focus distance of the cameras at snapshot f/stop was around 4 feet, and people often shot too close, and got out of focus images. Same with 110 Instamatics with fixed focus lenses-those had focus in to about 3 feet, which was too long of a minimum focus distance! TOo many OOF snapshots!

When people photographed babies, or flowers, or close-ups of whatever using their 126 or 110 cartridge load cameras, there were MANY OOF images. Kodak realized, they needed to invent a super-SMALL format, and the Disc Format was born. Focused at 3 feet, with its ultra-short lens (I think it was 3.5mm or 3.7mm) and teeny-tiny film size, which is interestingly about the same size we today specify as 1/1.7" size (ie-more or less what we now think of as _small-sensor digicam sized_), the Kodak Disc Camera fixed-focus lens was set at 3 feet, which was the hyperfocal focusing distance for that lens and that size of film format at the single, fixed f/stop the cameras used, and BOOM! Deep of field from here to yonder!

FOCUS-FREE photography was achieved with the Kodak Disc Camera format--based ENTIRELY on "optics". The laws of optics. With that small a format and that short of a normal lens, there was NO need for focusing the lens...anything that the camera was aimed at would pretty much be in good focus. (This is basically the recounting of Modern Photography's former editor Herbert Keppler's account of how Kodak engineers invented the Disc format--as a way to solve an actual problem by REDUCING format size and going to an ULTRA-short focal length standard lens!)


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## JacaRanda (Dec 31, 2013)

Derrel said:


> There **is a significant, noticeable and a very, real difference** between shooting with an APS-C or other smaller-sensor digital camera, and a 35mm-sized or 24mm x 36mm sensor camera( called FX by Nikon, or FF, AKA full-frame digital by many) as well as between a 35mm sensor size camera, and a medium-format rollfilm type camera, like say a 6x6 square camera like a Hasselblad. Mamiya, or Rollei,etc..
> 
> The simplest explanation is that the smaller the sensor or film size, the MORE depth of field there is at each picture "angle". Let's say we want to make a normal-lens picture--not an ultra-telephoto, tightly frames image, and not an ultra wide-angle panoramic image, just a normal picture. A point and shoot with a teeny-tiny sensor has almost infinite depth of field with its normal lens; an 8x10 view camera has very little depth of field with its normal lens; in between those extremes, there is MORE depth of field at each picture angle of view, as the sensor or film size gets smaller.
> 
> ...



3 & 4 are all I need to know or think about.


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## imagemaker46 (Dec 31, 2013)

Judobreaker said:


> Solarflare said:
> 
> 
> > Judobreaker said:
> ...



Is this what I said?  If I use a camera that allows me the option of using my 300mm and gives me a 460mm to shoot with, or I use a camera with my 300mm that gives me a 300mm, and I crop it in photoshop I will end up with exactly the same size image as the first camera?


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## Derrel (Dec 31, 2013)

Yes, those are pretty good ones. But number 5 is worth looking at closely; in the REAL WORLD what happens is that as sensors get smaller, and their corresponding lenses get shorter, in ACTUAL living situations, at home, at work, in the park, in the back yard, whenever-those small-sensor cameras and their short lenses approach, or hit, the hyperfocal distance, what *those cameras create are deep depth of field pictures.
*
HERE is the issue, as I see it: With a crop-frame d-slr, when shooting indoors in a garage studio, to shoot a group of six people in a horizontal row, you need to use a short lens, like around 19mm to 28mm. WHat do you get? DEEP depth of field, so that the background paper or wall is IN SHARP FOCUS!

With an FX camera, and the SAME,exact group of people, you can just begin to throw the background paper out of focus, so it is less of a distraction.  Moving to medium format film, the background will be well and truly de-focused.

One of the things that "non-photographers" often like are *selective focus photographs*. Those types of pictures are, for the most part, IMPOSSIBLE to make with small-sensor P&S or cellphone cameras.

One of the things that advanced street/journalist shooters LOVE is the ability to use a small-sensor camera, like a 4/3 sensor or even a compact P&S camera with good lens, to get HUGELY DEEP depth of fieldf pictures, without the need for super-critically placed,exacting focusing distance setting!!!!

THE kind of Henri Cartier-Bresson-like "street" images, the Garry Winogrand-like 28mm street images...that whole school of street reportage/documentary/decisive moment/near versus far kind of shooting, is made easier with a SMALLER-format sensor tool. When the smallish 4/3 sensor cameras first made by Olympus hit the market, the documentary/street/subway/restaurant/photojournalistic type shooters were SOOOOOOOOOO Happy, due to the small cameras, short lenses, and the deep depth of field type pictures that those TOOLS made possible, in actual, real-world places.

If you need to shoot across a cafe table AND still maintain sharp, clear, focus 20 feet behind, you CAN do that with an iPhone camera. You can NOT do that with an FX Nikon and 24mm lens. Nope.


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## amolitor (Dec 31, 2013)

Judobreaker said:


> Solarflare said:
> 
> 
> > And what exactly focal length means depends upon sensor size. Thus DOF depends upon sensor size.
> ...



Actually, he didn't say that. Go read it again.


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## Ysarex (Dec 31, 2013)

Judobreaker said:


> .....The only reason that the DOF varies is because people generally tend to get closer to the subject when they are using a larger sensor.....



That's just flat-out wrong. Go back and read through the thread.

Joe


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## Ysarex (Dec 31, 2013)

Derrel said:


> Ysarex said:
> 
> 
> 
> ...



I just kept wanting to put the bleep things into and View-Master and it never did work.

Joe


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## Derrel (Dec 31, 2013)

Ysarex said:
			
		

> I just kept wanting to put the bleep things into and View-Master and it never did work.
> 
> Joe



Funny! Odd thing...when I was in my early 20's, I used to work for a camera store near Beaverton, Oregon. About 1/4 mile away was the View-Master factory. Anyway,since View-Masters were made here locally, we had a few regular customers who were really huuuuge fans of stereo photography, and one older gentleman in particular worked at the View-Master plant and occasionally he would bring in View-Masters and custom discs he had shot AND HAD MADE AT WORK! He used old Stereo Realist cameras. 

It was soooo cool to see Columbia Gorge waterfall shots, and Rose Parade floats, and just local, Oregon coast shots and Willamette Valley shots all done by a really skilled shooter, and made in the current era!

Anyway, the View-Master process was invented right here in town in 1939 by Bill Gruber, a Portland photographer. So, every time I see a View-Master at Goodwill, I think back not to the ones I had as a little kid, but to the discs I saw made 20+ years later by a fellow from Beaverton.View-Master factory supply well - Wikipedia, the free encyclopedia

But yeah, I think Kodak's engineers might have thought about the View-Master disc system, but then again, there WAS an old-timey revolver-like camera that used a revolving disc film system, wayyyyy back in the 1910's I believe.


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## Ysarex (Dec 31, 2013)

Derrel said:


> Ysarex said:
> 
> 
> 
> ...



Oh I'm jealous! I loved View-Master. I used to have one and it went to Goodwill. Now that I'm retired I just might see about picking one up again. I could go spend my retirement account on ebay buying disks.

Joe


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## Ysarex (Dec 31, 2013)

Judobreaker said:


> Solarflare said:
> 
> 
> > Judobreaker said:
> ...



Do this:

Put a tripod on the ground in front of an immoveable subject.
Put the D800 along with an FX zoom on the tripod.
Frame your photo and note the framing carefully.
Focus on the subject.
Take the photo and remember the f/stop.
Put the D7000 on the tripod and do not move the tripod so much as a mm.
Take the zoom lens off the D800 and put it on the D7000.
Zoom the lens to frame the exact same photo you just took with the D800.
Focus on the subject (same focus distance as previous photo).
Take the photo using the same f/stop.

The photo taken with the D7000 has more DOF. If you don't think that's the case then you need to adjust you're thinking.

Joe


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## Judobreaker (Jan 1, 2014)

Yes of course it differs, I don't even have to test this. You're changing the lens physics to a different length.
It's still not the sensor that gives you a smaller DOF in that case, it's the different focal length of the lens.

My point is that the size of the sensor itself has no effect on DOF whatsoever.
Try this:

Put a tripod on the ground in front of an immoveable subject.
Put the D800 along with an FX *fixed* lens on the tripod.
Frame your photo.
Focus on the subject.
Take the photo and remember the f/stop.
Put the D7000 on the tripod and do not move the tripod so much as a mm.
Take the lens off the D800 and put it on the D7000.
Focus on the subject (same focus distance as previous photo).
Take the photo using the same f/stop.
Load the D800 image in Photoshop (or any image processing software for that matter).
Crop the image with a factor of 0.625 (1.6x in reverse, to get from FX to DX format).

And now tell me if the DOF is still thinner.


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## Ysarex (Jan 1, 2014)

Judobreaker said:


> Yes of course it differs, I don't even have to test this. You're changing the lens physics to a different length.
> It's still not the sensor that gives you a smaller DOF in that case, it's the different focal length of the lens.
> 
> My point is that the size of the sensor itself has no effect on DOF whatsoever.
> ...



And you're taking two different photos. If you read through the thread the point was stressed over and over that if you take *THE SAME PHOTO* with two different size sensors the smaller sensor photo will have more DOF. No one ever said it was a direct function of the sensor. In fact that was also made clear; the relationship is indirect but it is no less real. It is correct to say that in general when you use smaller sensor cameras you get more DOF. And it is most certainly not because people with larger sensor cameras get closer to their subject.

Joe

EDIT: Sorry, I didn't carefully read through your list. If you're going to crop the D800 sensor down then it's not a D800 any more it's just a D7000 in which case a D7000 has the same DOF as a D7000 -- duh. You have to use each camera's full sensor for the photo otherwise you're not comparing different size sensors are you.


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## Judobreaker (Jan 2, 2014)

Ysarex said:


> And you're taking two different photos. If you read through the thread the point was stressed over and over that if you take *THE SAME PHOTO* with two different size sensors the smaller sensor photo will have more DOF. No one ever said it was a direct function of the sensor. In fact that was also made clear; the relationship is indirect but it is no less real. It is correct to say that in general when you use smaller sensor cameras you get more DOF. And it is most certainly not because people with larger sensor cameras get closer to their subject.



Of course it is because people with a larger sensor get closer to their subject... That is the only explanation when we're assuming you use the same lens.
Either you get closer or you use a longer focal length, but in both cases it is not the sensor size that changes the DOF... That is simply impossible.





Ysarex said:


> EDIT: Sorry, I didn't carefully read through your list. If you're going to crop the D800 sensor down then it's not a D800 any more it's just a D7000 in which case a D7000 has the same DOF as a D7000 -- duh. You have to use each camera's full sensor for the photo otherwise you're not comparing different size sensors are you.



I'm cropping a photo made with the sensor of a D800. If the cropped D800 and the uncropped D7000 are exactly the same than that proves sensor size doesn't change DOF right? Unless in some magical way I can change my DOF by cropping a photo in Photoshop...


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## amolitor (Jan 2, 2014)

The exact same argument can be made to _prove_ that nothing at all changes DoF.


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## Ysarex (Jan 2, 2014)

Judobreaker said:


> Ysarex said:
> 
> 
> > And you're taking two different photos. If you read through the thread the point was stressed over and over that if you take *THE SAME PHOTO* with two different size sensors the smaller sensor photo will have more DOF. No one ever said it was a direct function of the sensor. In fact that was also made clear; the relationship is indirect but it is no less real. It is correct to say that in general when you use smaller sensor cameras you get more DOF. And it is most certainly not because people with larger sensor cameras get closer to their subject.
> ...



*You* are assuming the same lens. *We* are not. *We* have all along been assuming that we are using the two different sensor cameras to take *the same photograph.* We made that very very clear. When I first corrected you I said, "Assumption:  You want to take the exact same photo with two different cameras that  have different size sensors." In order to do that the two cameras must be placed in the same physical location. We know what we have been talking about all along. Read the thread.



Judobreaker said:


> Either you get closer or you use a longer focal length, but in both cases it is not the sensor size that changes the DOF... That is simply impossible.



And no one in this thread has ever said that or made that claim -- at least I haven't.

Again in the post where I first corrected you I said, "Now it's not that DOF is a function of sensor size directly. It's an indirect effect but no less real. *It's this: In simplest form DOF = f/stop + magnification.*  When you do the math on magnification and factor in that you're using  the cameras to take the exact same photo, you must get more DOF from  smaller sensor cameras and less DOF from larger sensor cameras."

When I corrected you then I clearly affirmed the working assumption: *TAKE THE SAME PHOTO.*

With both cameras in general use the camera with the smaller sensor must produce photos with more DOF. That is because the smaller sensor plays a role in setting the practical limits of magnification. When *the same photo* is taken with two different cameras using different size recording media the photo from the camera with the smaller media will have more DOF. That's the claim that I have made. I have made no other claim. That claim is correct.

AND going all the way back to the OP's original post he gives the example of crop factors being used to compare focal length lenses between formats. AND THAT'S BECAUSE when people use different format size cameras they change lenses!! They do that in order to be able to *TAKE THE SAME PHOTOS!* A 50mm is commonly used with crop sensors to take portraits. Photographers don't put a 50mm on a FF sensor and get closer to take a portrait. They stay in the same place and use an 85mm!! And one of the big reasons they chose that FF camera for portraits in the first place is because they want the reduction in DOF that comes with using a larger sensor!!!

Joe


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## Judobreaker (Jan 2, 2014)

Your first post in this topic.



Ysarex said:


> Yep, I agree it's way past time to put the whole 1.6 times and focal length equivalent nonsense away. There are however real differences in the kinds of photos you can take one format size to another and it's valuable to be aware of those differences. *For example there are real differences in how DOF is going to work as you increase or decrease the size of the sensor.*
> 
> Joe


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## Derrel (Jan 2, 2014)

Judobreaker said:


> Your first post in this topic.
> 
> 
> 
> ...



Not to speak for Joe, or in Joe's defense, because he's a big boy and has forgotten more about photography than many people here have managed to learn, but YEAH, his first post pretty much sums it up. There are very real differences in how much depth of field a person has available to him, based on how large the film format, or sensor format, happens to be. Having shot 4x5 sheet film, 6x9 cm, 6x6 and 6x4.5 cm rollfilm, 135 size film AKA "35 millimeter fullframe" film and digital, as well as 1.5x Nikon and 1.6x Canon d-slr, plus 1/2.3" [sic] digital P&S, and diminutive iPhone, I'm pretty damned familiar with HOW depth of field is VERY limited on 4x5 unless camera movements are used, becomes less-limiting on medium format, is not that big an issue on 645, and on 35mm full-frame is easy to work with, and how on 1.5x and 1.6x and smaller, depth of field becomes basically TOO GREAT for the kinds of pictures I want to make much of the time.

If one does not KNOW,as in KNOW intimately and without doubt or confusion, from ACTUAL, you know,* hands-on experience*, that a SMALLER film size, or a SMALLER digital sensor, gives more depth of field in the same "circumstances" than does a larger-format camera, it might be advisable to just sit back and not make any foolish statements about how there's no difference in DOF behavior between cameras of different format sizes.

Anyway, earlier this AM I made some screen caps. Just wanted to show how foolish some people look. Here are the cold, hard numbers, in which we use two camera formats, and the same lens focal length, an 85mm lens, to frame the SAME EXACT scene. Now, imagine this is at a wedding, in a crowded reception area. With one camera, you stand 20 feet or so away...with the 1.6x Canon, you are forced to stand over 30 feet distant.








See how this shakes out in the REAL world????


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## Ysarex (Jan 2, 2014)

Judobreaker said:


> Your first post in this topic.
> 
> 
> 
> ...



Yep. I was correct then and I remain correct now. I said there are real differences in how DOF is going to work with changes in the size of the sensor. That's a correct statement though not very detailed. I DID NOT say that DOF is a direct function of sensor size. I did later clarify that sensor size indirectly effects DOF and I'm right. It does. One of the reasons photographers purchase and use larger sensor cameras is so they can take advantage of the ability they get from those cameras to better control selective focus (DOF). You say you have a D800 and you're not aware of that?!! One of the persistent complaints that you hear from people with smaller sensor cameras is that they can't get the same degree of selective focus (DOF) that they see from FF cameras. They can't, and guess why? You're going to say because they're standing too far back and they should move forward like people who use FF cameras do?

So how many times do you need to have this repeated: Take the same photo (same f/stop) with two cameras that have different size sensors and the photo taken by the camera with the smaller sensor will have more DOF. And that is a *real difference in how DOF works as you increase or decrease the size of the sensor.* Go to DOFMaster and run the simulations if you need more help.

Joe


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## Ysarex (Jan 2, 2014)

Derrel said:


> Not to speak for Joe, or in Joe's defense, because he's a big boy and has forgotten more about photography than many people here have managed to learn, but YEAH, his first post pretty much sums it up. There are very real differences in how much depth of field a person has available to him, based on how large the film format, or sensor format, happens to be. Having shot 4x5 sheet film, 6x9 cm, 6x6 and 6x4.5 cm rollfilm, 135 size film AKA "35 millimeter fullframe" film and digital, as well as 1.5x Nikon and 1.6x Canon d-slr, plus 1/2.3" [sic] digital P&S, and diminutive iPhone, I'm pretty damned familiar with HOW depth of field is VERY limited on 4x5 unless camera movements are used, becomes less-limiting on medium format, is not that big an issue on 645, and on 35mm full-frame is easy to work with, and how on 1.5x and 1.6x and smaller, depth of field becomes basically TOO GREAT for the kinds of pictures I want to make much of the time.



Hmmm... Derrel speaking for me? I'll have to think about that.

Yeah I used to shoot portraits with 4x5 sheet. f/11 on a head and shoulders wouldn't keep you sharp from the tip of their nose to their eyes yet alone back to an ear. Now I take a head and shoulders of my wife with my little compact and f/4.5 still has the bookcase behind her in focus.

Joe


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## rambler (Jan 2, 2014)

Suppose you set up a 4/3 next to a full frame camera and took the shot using the same exposure equivalent focal distance for example 50mm on the full frame would be 100mm on the 4/3.   I believe you would see more included in the full frame because the edges would be further apart than on the 4/3.  But, you could achieve the same look with the 4/3 just by backing up several feet.  The term "cropped" is just to make it a bit easier to visualize the difference between the two original shots.  It just looks as though one must have "cropped" off the edges of the full frame result.  However, nothing has actually been cropped.  You are just looking at the results of two different sized sensors.  Hmm. could someone here actually do this?  

Take a look here:
http://www.kenrockwell.com/tech/crop-factor.htm


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## Judobreaker (Jan 3, 2014)

Oh don't worry, I understand completely what you guys are trying to say. Of course I know that it is much easier to achieve a thinner DOF with my D800 (although that is not the main reason I bought it, it can be pretty neat though).
I just simply can't agree with the statement that sensor size has an effect on how DOF works, because that is physically impossible.
I fully agree on the fact that with an FX sensor you'll usually get closer or use longer lenses and your DOF will be thinner as a result, but that is a result of the lens. That may be labelled as an indirect effect of the sensor size, sure I won't disagree on that, but theoretically speaking it is still not the sensor that has the actual effect. 
I suspect we're going to have to agree to disagree on that statement, even though we probably agree on how it actually works. xD


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## Helen B (Jan 3, 2014)

The sensor size has an effect on the MACC (maximum acceptable circle of confusion) at the camera's image plane for any given final image size and desired resolution (MACC at the final image size) because of the degree of magnification from the camera image to the final image. 

For a given, fixed perspective (camera position), focus distance and angle of view (ie "same picture" criterion) the sensor size will affect the focal length. The focal length affects the DoF, as does the MACC. I don't think Ysarex has suggested anywhere that the sensor size, per se, has a direct effect on DoF, but it does have an effect, as he says.


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## amolitor (Jan 3, 2014)

Oh, so you admit that you're just being an obnoxious pedant for the purpose of maintaining a fight about.. nothing, Judobreaker? Ok then.


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## Ysarex (Jan 3, 2014)

Judobreaker said:


> Oh don't worry, I understand completely what you guys are trying to say. Of course I know that it is much easier to achieve a thinner DOF with my D800 (although that is not the main reason I bought it, it can be pretty neat though).
> I just simply can't agree with the statement that sensor size has an effect on how DOF works, because that is physically impossible.
> I fully agree on the fact that with an FX sensor you'll usually get closer or use longer lenses and your DOF will be thinner as a result, but that is a result of the lens. That may be labelled as an indirect effect of the sensor size, sure I won't disagree on that, but theoretically speaking it is still not the sensor that has the actual effect.
> I suspect we're going to have to agree to disagree on that statement, even though we probably agree on how it actually works. xD



No, I don't have to agree to disagree, you are wrong. Any practical use of DOF while working with a camera includes accounting for the magnification limits enforced pragmatically by the sensor size.

I do however agree with Andrew.

Oh, and I'm not worried.

Joe


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## Ysarex (Jan 3, 2014)

Judobreaker said:


> Oh don't worry, I understand completely what you guys are trying to say. Of course I know that it is much easier to achieve a thinner DOF with my D800 (although that is not the main reason I bought it, it can be pretty neat though).
> I just simply can't agree with the statement that sensor size has an effect on how DOF works, because that is physically impossible.
> I fully agree on the fact that with an FX sensor you'll usually get closer or use longer lenses and your DOF will be thinner as a result, but that is a result of the lens. That may be labelled as an indirect effect of the sensor size, sure I won't disagree on that, but theoretically speaking it is still not the sensor that has the actual effect.
> I suspect we're going to have to agree to disagree on that statement, even though we probably agree on how it actually works. xD



Just one more thing. There is obviously a clear consensus here that you are wrong. Derrel has told you you're wrong. I have told you you're wrong. Andrew has told you you're obnoxious, etc. etc.

But please note: *Helen has now told you you're wrong.* Hopefully you've been around here long enough to know that once Helen tells you you're wrong it's over. Should you proceed in the face of that with the "agree to disagree" BS you'll be a whole lot more than just wrong and obnoxious. Just lookin' out for you here.

Joe


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## runnah (Jan 3, 2014)

amolitor said:


> There was a time when it made sense, when they were building 35mm film cameras, and crop-sensor DSLRs, simultaneously. They did, at that time, need to emphasize to 35mm film shooters that while their existing lenses WOULD work on the new digital bodies, there was gonna be a difference in field of view. That was a very specific marketing tactic for a very specific interval in the industry.
> 
> It's no longer relevant, and it creates far more total confusion than clarification now.



Well I think this summed things up nicely.


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## Judobreaker (Jan 4, 2014)

Ysarex said:


> Judobreaker said:
> 
> 
> > Oh don't worry, I understand completely what you guys are trying to say. Of course I know that it is much easier to achieve a thinner DOF with my D800 (although that is not the main reason I bought it, it can be pretty neat though).
> ...



Everybody laughed at Columbus because he said the world was round. That didn't make him wrong did it? 

I stand by my statement that sensor size itself does not affect DOF, whatever you guys say. It is simply physically impossible that sensor size affects the DOF.
Yes, you guys are correct by saying that people tend to change other factors because of the larger sensor (focal length, subject distance), however that only means it has an effect on the shooter, not on the DOF itself.

The DOF of an image coming from a camera is determined by aperture, focal length, subject distance and sensor resolution. Sensor size does not matter.


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## Sventek (Jan 4, 2014)

People might be interested in this: Image sensor format - Wikipedia, the free encyclopedia


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## Ysarex (Jan 4, 2014)

Judobreaker said:


> Ysarex said:
> 
> 
> > Judobreaker said:
> ...



People change other factors* within the limits of what is possible*. You can't move mountains to take a photograph and moving yourself relative to a mountain range isn't going to count for squat. All through this thread words like practical and pragmatic have been used because the limits of what is possible are pragmatically real. DOF in use is pragmatically real as well.

Where
H = hyperfocal distance
f = lens focal length
N = f/stop
c = circle of confusion (tied to sensor size).



That is the standard formula for calculating hyperfocal distance. Please demonstrate with examples of how you can alter only the value of c without effecting the value of H and you get to be right. Otherwise you continue to stand corrected. It's math 1, you 0. And now you're lookin' like more than just wrong.

Joe


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## Derrel (Jan 4, 2014)

Judobreaker said:
			
		

> Everybody laughed at Columbus because he said the world was round. That didn't make him wrong did it?
> 
> I stand by my statement that sensor size itself does not affect DOF, whatever you guys say. It is simply physically impossible that sensor size affects the DOF.
> Yes, you guys are correct by saying that people tend to change other factors because of the larger sensor (focal length, subject distance), however that only means it has an effect on the shooter, not on the DOF itself.
> ...



Judobreaker, I think Janice said it best:


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## sleist (Jan 4, 2014)

Judobreaker said:


> I stand by my statement that _*sensor size itself*_ does not affect DOF, whatever you guys say.
> 
> [SNIP]
> 
> The DOF of an image coming from a camera is determined by aperture, focal length, subject distance and sensor resolution. Sensor size does not matter.



You are contradicting yourself within the same post.
The bolded (by me) text in your first statement can be interpreted to imply that sensor size _*can*_ impact DOF.
To go on to say that _*sensor size does not matter*_ is a contradiction.

You seem to be arguing both sides whenever it seem convenient to do so.


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## amolitor (Jan 4, 2014)

Judobreaker said:


> Everybody laughed at Columbus because he said the world was round. That didn't make him wrong did it?



Interestingly, everyone knew the world was round, and about how big it was. Columbus sold a story about how, sure it's round, but it's a lot smaller than everyone says, so China is basically _right there_. In fact that is almost no way Columbus didn't also know how big the earth was, so he was almost certainly selling a bogus story about China in order to fund an expedition to whatever it was that was most likely right out there.



Judobreaker said:


> I stand by my statement that sensor size itself does not affect DOF, whatever you guys say. It is simply physically impossible that sensor size affects the DOF.



Yes, you're standing by an accurate statement that has nothing whatsoever to do with what's being talked about, because you want to keep fighting, because you're that kind of guy. Why don't you stand by the statement that some trees are pretty tall, or that some people are combative idiots? That would be exactly as relevant.

Your argument can be used to show that no other single factor affects DoF either. Aperture doesn't affect DoF because if I use some other camera and some other lens to take some different picture it has exactly the same DoF, so aperture is out. Ditto subject distance. Ditto magnification.

THEREFORE DOF IS A UNIVERSAL CONSTANT! WOOO!


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## manaheim (Jan 4, 2014)

I think this discussion has run its course, and has delved well into the depths of ridiculousness.

My advice, to everyone involved, would be to weigh the amount of those arguing for or against the DOF being affected by crop sensors, and then re-evaluate your own position based upon the total mass on either end of that scale.


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