# A look at lens sharpness



## fmw (Aug 22, 2016)

Deleted to satisfy critics.


----------



## smoke665 (Aug 22, 2016)

Interesting. I've really been torn between a fixed or zoom for a macro. After seeing this, I'm leaning toward a fixed.


----------



## fmw (Aug 22, 2016)

That would depend on the particular zoom, of course.  Understand that "macro" zoom lenses don't focus as closely real macro lenses and all the real macro lenses are fixed focal length.  Mine, for instance will handle a 1:1 reproduction ratio or life size in the frame.  Most "macro" zooms can only do about 1:4.


----------



## astroNikon (Aug 22, 2016)

The D800 really pushed lens quality when it first came out.

DxO mark identifies the resolved resolution of lenses so one can compare to the sensor resolution.
such as this example of the 60mm and d7000 ==> Nikon AF-S Micro NIKKOR 60mm f/2.8G ED mounted on Nikon D7000 : Tests and Reviews  | DxOMark


----------



## smoke665 (Aug 22, 2016)

fmw said:


> macro" zoom lenses don't focus as closely real macro lenses



I'm finding that out. In Pentax line, 35mm macro limited will go down to about 6". The 100mm is double that at 12". Both are 1:1. Zooms are closer to 15"


----------



## Tim Tucker (Aug 23, 2016)

Given that distance to subject affects lens performance it's no real surprise that when you set it to very close focus the dedicated macro prime lens wins against an expensive zoom and a known old crock. 

And f18 on a DX sensor? Again the macro prime will perform much better at smaller apertures than the zooms because it's design is not as limited by the effects of diffraction.

Is this really an accurate guide to lens sharpness, or are you just saying that a lens that's specifically designed for close focus work at small apertures works better at close focus and smaller apertures than ones that aren't?


----------



## fmw (Aug 23, 2016)

astroNikon said:


> The D800 really pushed lens quality when it first came out.
> 
> DxO mark identifies the resolved resolution of lenses so one can compare to the sensor resolution.
> such as this example of the 60mm and d7000 ==> Nikon AF-S Micro NIKKOR 60mm f/2.8G ED mounted on Nikon D7000 : Tests and Reviews  | DxOMark



I'm not sure what this tells me.  Also it isn't the same lens I used.  To compound my confusion, a D800 image cropped to DX format has about the same pixel density.


----------



## fmw (Aug 23, 2016)

smoke665 said:


> fmw said:
> 
> 
> > macro" zoom lenses don't focus as closely real macro lenses
> ...



How closely they will focus depends both on the macro focusing capacity and the focal length.  The issue is the reproduction ratio.  Since both of your lenses produce 1:1 it is perfectly natural that the longer lens will be further from the subject at that ratio.


----------



## fmw (Aug 23, 2016)

Tim Tucker said:


> Given that distance to subject affects lens performance it's no real surprise that when you set it to very close focus the dedicated macro prime lens wins against an expensive zoom and a known old crock.
> 
> And f18 on a DX sensor? Again the macro prime will perform much better at smaller apertures than the zooms because it's design is not as limited by the effects of diffraction.
> 
> Is this really an accurate guide to lens sharpness, or are you just saying that a lens that's specifically designed for close focus work at small apertures works better at close focus and smaller apertures than ones that aren't?



You misunderstand.  All of these lenses were focused from about the same distance.  The original image includes the entire placemat on all three lenses.  You are looking at a crop of the image, not a closeup.  The test is quite valid.

f18?  That is what is needed to get a proper exposure with my strobes at minimum power and no ND filter.  Also it ensures that everything is in acceptable focus so it is a standard setup for product photography for me.

If you are worried about diffraction, then how do you explain that all three were shot at the same aperture?  Diffraction is aperture dependent.  Also the expensive zoom has many more elements than the cheap one so issues such as diffraction or flare would affect it more.  Diffraction is one of the most overblown concerns of amateur photographers.  There is no effect of diffraction in any of these images.

Finally it isn't a guide to lens sharpness.  It is a demonstration for beginners (this is the beginner forum) about how lens quality matters and, in fact, matters more than sensor resolution.  The lens forms the image.  The sensor merely captures it.  A great sensor can't fix a poorly formed image.


----------



## robbins.photo (Aug 23, 2016)

fmw said:


> Finally it isn't a guide to lens sharpness.



Then why is the title of the thread "A Look At Lens Sharpness"?

Also, note this little gem from your original posting:

"If we were looking at the entire frame, the image would look sharp to us."

Isn't that what we should be looking at?  As long as the image itself as it was meant to be presented is sharp, isn't that really what should be of concern to most folks?

Is there really any point at all to go pixel peeping to specifically find issues that can't really be seen when the photograph is viewed as intended?


----------



## Tim Tucker (Aug 23, 2016)

fmw said:


> All of these lenses were focused from about the same distance.



Yes, and lens performance varies between close focus-middle distance-infinity. I would expect the zoom lenses to perform much better between portrait distance and infinity.




fmw said:


> If you are worried about diffraction, then how do you explain that all three were shot at the same aperture? Diffraction is aperture dependent.



Yes, and no. Yes diffraction is aperture dependant, and no they were not all shot at the same _actual_ aperture. The f-stops on your lens are not _actual_ aperture but _effective_ aperture. Consider the new Nikkor 105/1.4, how do you think they fit an actual aperture of 75mm plus enough room for the aperture blades when fully open? They don't.

Here is a very simple explanation:






For a simple lens the _effective_ aperture is the restriction for parallel rays entering the lens. But look what happens when you move the diaphram to the other side of the lens. Because the lens bends the light the actual aperture is much smaller to create the same restriction. Compound lenses all squeeze the light and the amount they squeeze it is dependant on specific lens design. So the _actual_ aperture needed to produce the same _effective_ aperture varies with lens design and so do the effects of diffraction.



fmw said:


> Finally it isn't a guide to lens sharpness. It is a demonstration for beginners (this is the beginner forum) about how lens quality matters and, in fact, matters more than sensor resolution. The lens forms the image. The sensor merely captures it. A great sensor can't fix a poorly formed image.



Within reason. The trouble with modern sensors is that they allow you to enlarge the image to ridiculous proportions. An enlargement that allows you to see tiny flaws and aberrations that are not visible at normal viewing distances. Nearly all modern lenses will produce sharp enough images, they do not create poorly formed images when used correctly. So I do not think a beginner should worry or fuss about absolute sharpness at 100% magnification but rather how to make their finished images appear sharp by concentrating on technique as well. The newest lens in my bag for the D600 is from 1975. With my 1973 35mm/f2 I use I've never one had anybody comment on it's lack of sharpness, even though in tests it's no comparison to a Sigma Art. Lens performance is not as important in making sharp images as people think unless you live at the edge of a lens' performance.


----------



## fmw (Aug 23, 2016)

You exhausted me.  I give up and withdraw my post.


----------



## fmw (Aug 23, 2016)

robbins.photo said:


> fmw said:
> 
> 
> > Finally it isn't a guide to lens sharpness.
> ...



No reason.  Time to trade my lens for a kit lens.  How silly of me to want to give information to beginners.


----------



## robbins.photo (Aug 23, 2016)

fmw said:


> robbins.photo said:
> 
> 
> > fmw said:
> ...



Ok, not sure why the need to play the victim card here.  I'm just asking a couple of basic questions.  One, if your intent was not to discuss lens sharpness then why does the title pretty much give folks the exact opposite impression?  

And two, what is the ultimate purpose of this since you yourself stated that the image looks sharp when viewed as intended.  So if it looks sharp when it's viewed as intended, what purpose does this pixel peeping stuff ultimately serve?

If this is, as you maintain, quality information that beginners need to know then why would it be at all difficult to answer these questions?


----------



## Ysarex (Aug 23, 2016)

smoke665 said:


> Interesting. I've really been torn between a fixed or zoom for a macro. After seeing this, I'm leaning toward a fixed.



Careful there. All he's done is demonstrate that when you look at the sh*ty JPEGs from his camera one of his zooms is a dog. There are so many complicating factors that aren't addressed in the original post. Sharpness is a complex topic that involves a lot more than just lens resolution. As Tim already noted there's a concern with diffraction. In the digital world complications ramp up: photos are shot through a CFA so you've got demosaicing to deal with and then the AA filter (or not) on top of that and that's just for starters.



 

That's a 100% crop using the macro function of my Schneider zoom lens. Wouldn't surprise me at all if it's a sharper lens than the 60mm Micro Nikkor. Generalizations do have some value as rough guides but caution is the rule. You can consider a generalization but be very careful before applying one.

Joe


----------



## fmw (Aug 23, 2016)

robbins.photo said:


> fmw said:
> 
> 
> > robbins.photo said:
> ...




They aren't hard to answer.  They have no meaning to me.  I promise not to start any more threads in the beginner forum.


----------



## fmw (Aug 23, 2016)

Ysarex said:


> smoke665 said:
> 
> 
> > Interesting. I've really been torn between a fixed or zoom for a macro. After seeing this, I'm leaning toward a fixed.
> ...



Exactly my point.  Now, what makes my JPEGS sh*ty?


----------



## Ysarex (Aug 23, 2016)

fmw said:


> Ysarex said:
> 
> 
> > smoke665 said:
> ...



They're camera generated JPEGs.

Joe


----------



## robbins.photo (Aug 23, 2016)

fmw said:


> robbins.photo said:
> 
> 
> > fmw said:
> ...



Fred, if you send me your address I'll be more than happy to send you a box of tissues.

You've tried to portray me twice now as some big bully who doesn't want you to talk to beginners - but the truth is I'm just asking a very straight forward question that you can't seem to answer.

What good is this information for beginners?  Or anyone really?  What purpose does it serve?   If the photo appears sharp when viewed as intended, what purpose does this pixel peeping serve?  It pretty much goes right to the heart of the matter, and yet it's a question you say "has no meaning" for you.

So really what was the point of the thread in the first place?


----------



## fmw (Aug 23, 2016)

Ysarex said:


> fmw said:
> 
> 
> > Ysarex said:
> ...


And what causes them to invalidate the images?


----------



## fmw (Aug 23, 2016)

robbins.photo said:


> fmw said:
> 
> 
> > robbins.photo said:
> ...


----------



## jcdeboever (Aug 23, 2016)

Tim Tucker said:


> fmw said:
> 
> 
> > All of these lenses were focused from about the same distance.
> ...


Excellent, informative, and useful.


----------



## jcdeboever (Aug 23, 2016)

fmw said:


> robbins.photo said:
> 
> 
> > fmw said:
> ...


I'm glad you did. Useful info. You brought up an interesting topic and additional info was added.


----------



## KmH (Aug 23, 2016)

Tutorials – Sharpness


----------



## Overread (Aug 23, 2016)

Tim Tucker said:


> Yes, and no. Yes diffraction is aperture dependant, and no they were not all shot at the same _actual_ aperture. The f-stops on your lens are not _actual_ aperture but _effective_ aperture. Consider the new Nikkor 105/1.4, how do you think they fit an actual aperture of 75mm plus enough room for the aperture blades when fully open? They don't.



I was under the impression that Nikon lenses (at least own brand) actually do show the effective aperture to the user. Which is why an f2.8 macro from the Nikon line can only use around f4 or smaller apertures at their 1:1 focusing distances, whilst Canon lenses (which do not show effective aperture) can be set to f2.8. Even though in reality both lenses (if of comparable design and focal length) are likely using the very same effective aperture.


As a result the rough limit on sharpness before diffraction causes noticeable harm tends to be around f13 to f16 on my Canon lenses which is likely closer to around f18 or so on Nikon brand options reporting the effective aperture. Thus the use of f18 might not be as bad as some are thinking; or at least its more at the general limit of acceptable sharpness most accept (or at least at the point where diffraction softening starts to become more noticeable). 

Although as said resizing, such as for internet display, can very easily make it possible to use smaller apertures (bigger f numbers) and still get a resized shot that looks acceptably sharp.


----------



## Ysarex (Aug 23, 2016)

fmw said:


> Ysarex said:
> 
> 
> > fmw said:
> ...



Since all were from the same camera (and we assume similarly processed) you can claim some validity in comparing three of your lenses used in that one condition. But the camera JPEGs are poor illustrations of the sharpness your lenses are achieving.

Let's try an analogy: you want to purchase a guitar and have two to choose from. You are concerned about how they sound but are not able to travel to actually try them out so your best option is to listen to a recording. Would you prefer a recording made sloppily in the shop with a phone or a recording made carefully with good recording equipment?

All digital photos must be sharpened in processing which begins with the choice of demosaicing algorithm and parameters for that algorithm. All through the process to the point of final output there are choices to make that involve sharpness. Camera JPEGs are made quickly with minimal processing power available and generic "one-size-fits-all" algorithms that are globally applied in a single step. You have only a single option on the camera to set a value for sharpening and then only the ability to set a single numeric value -- that's pretty crude. Odds are they could be a lot better.

Joe


----------



## fmw (Aug 23, 2016)

The jpegs were fine for making my point.  You simply missed my point.


----------



## robbins.photo (Aug 23, 2016)

fmw said:


> The jpegs were fine for making my point.  You simply missed my point.



Well truthfully Fred so did I - but when I asked you to explain your point instead you played the victim card and have pretty much continued to do so.  

So what you illustrated was that under similar conditions if you pixel peep shots with various lenses you will see a difference.  But ultimately even you yourself stated that if you don't pixel peep the images look fine.

So again I'm left wondering what was the purpose of the comparison?


----------



## Tim Tucker (Aug 23, 2016)

Overread said:


> I was under the impression that Nikon lenses (at least own brand) actually do show the effective aperture to the user. Which is why an f2.8 macro from the Nikon line can only use around f4 or smaller apertures at their 1:1 focusing distances, whilst Canon lenses (which do not show effective aperture) can be set to f2.8. Even though in reality both lenses (if of comparable design and focal length) are likely using the very same effective aperture.



I think all lenses show effective aperture expressed as an f-stop (or ratio between focal length and effective aperture) and none show actual aperture, as it's fairly meaningless on it's own and actually varies quite dramatically in different designs of the same focal length. I think the f4 comes from the lens design itself, at close focus the lens can be effectively double the focal length and what was a ratio of 1:2.8 becomes 1:4.


----------



## Ysarex (Aug 23, 2016)

fmw said:


> The jpegs were fine for making my point.  You simply missed my point.



I don't think so but that's kind of moot now since you deleted it. I first responded to another poster who got some kind of point from your post and that raised a red flag for me. I saw this other poster looking at what you presented and saying that it was swaying his possible future purchase decision. That's why I jumped in. I was concerned that he was being potentially misled with potential costly consequence.

As for sh*ty JPEGs why did you post them if not as illustrations. Here's an example of how sh*ty they are:




 

This site posts reviews and sample files: Nikon D7000 Review - Sample Images | PhotographyBLOG

I downloaded one of the JPEG/raw pairs -- how do you examine the issue of lens sharpness when you've allowed the camera software to sh*t all over the photo?

Joe


----------



## Overread (Aug 23, 2016)

JPEG with standard sharpness and in-camera settings set to neutral values is a good way to measure sharpness in my view. If you want to show raws try turning off sharpening in RAW processing and you'll nearly always get a shock how soft RAWs are without any sharpening at all.

But that's the thing RAWs are all over the place with different settings - standard JPEG is a good measure that; for a layperson test that isn't trying to be highly scientific but to carry a point that is valid. Especially as most lay people can't own every camera body out there (nor even a majority) in order to develop a neutral workflow for RAW processing that is faithful to the quality adjustments being shown.


----------



## fmw (Aug 23, 2016)

Tim Tucker said:


> I don't think so but that's kind of moot now since you deleted it. I first responded to another poster who got some kind of point from your post and that raised a red flag for me. I saw this other poster looking at what you presented and saying that it was swaying his possible future purchase decision. That's why I jumped in. I was concerned that he was being potentially misled with potential costly consequence.



He wasn't being misled.  Who are you to decide for him what he wants to buy?  I've had enough of amateur experts for today.


----------



## robbins.photo (Aug 23, 2016)

fmw said:


> He wasn't being misled.  Who are you to decide for him what he wants to buy?  I've had enough of amateur experts for today.



So... I guess we'll see you tomorrow then?


----------



## Tim Tucker (Aug 23, 2016)

fmw said:


> Tim Tucker said:
> 
> 
> > I don't think so but that's kind of moot now since you deleted it. I first responded to another poster who got some kind of point from your post and that raised a red flag for me. I saw this other poster looking at what you presented and saying that it was swaying his possible future purchase decision. That's why I jumped in. I was concerned that he was being potentially misled with potential costly consequence.
> ...




Whoa! I didn't say that, a mis-edit me thinks...

I disagree with you because the most common error I see beginners make is not understanding that there are practical limits to photography. For instance taking photos of 'your' kid's birthday by the light of the candles alone on full auto will test any gear. The problem is not that the lens is soft but that people do not realise that there are limits to which they can achieve sharp photos. Your (deleted) test showed an older, cheaper, zoom at probably it's least capable (close focus) against a lens specifically designed for the purpose. So to the beginner I say that you cannot just point your camera and expect technology to resolve the problems, there are practical limits to the gear you use. Better gear expands those limits but never removes them. I would teach the beginner to understand the limits that their gear performs well in. (Taking outstanding photos with poor and outdated gear is entirely about understanding the limits within which it performs well.)

P.S. Regardless of whether we agree or disagree there are some very useful points raised relevant to beginners, including the contributions by yourself.


----------



## gckless (Aug 24, 2016)

Awww, I missed the party 

TL;DR - sharpness isn't everything?


----------



## unpopular (Aug 24, 2016)

astroNikon said:


> The D800 really pushed lens quality when it first came out.



This seems kind of like a silly statement. Like when I bought a computer to "do anything I'd ever want to do" only to push what I want to do with it to the maximum capability of my computer to the point that I don't perceive any net performance gain. This is kind of the nature of things, of course, but I kind of doubt to some degree, anyway, that all *that*much has changed, only what we can realistically demand from a lens has.

Ofcourse, at the same time, this isn't film where the size of the medium changes whilst it's resolution stays constant. Film reached it's epoch long ago, and the only approach to improving resolution is to decrease enlargement. As a result, you can get away with much lower lens resolution using large format than you could with small format. Today, we're getting these crazy resolutions at the focal plane that are probably approaching the resolving power of 645, while the film gate remains constant - ever increasing what we demand from the lens.

Interestingly, it may be the physical capabilities and economics of lens design that pushes us forward into larger sensors.


----------



## smoke665 (Aug 24, 2016)

Ysarex said:


> I saw this other poster looking at what you presented and saying that it was swaying his possible future purchase decision. That's why I jumped in. I was concerned that he was being potentially misled with potential costly consequence.





fmw said:


> He wasn't being misled. Who are you to decide for him what he wants to buy?



Guys I wasn't misled. I probably should have stated my post differently. I haven't bought anything yet, as it seems that as soon as I save up enough "fun money" to buy, either the price goes up or my sights drift higher. Fred merely reminded me of something I had already read on a zoom vs fixed and some my own experiences.


----------



## Ysarex (Aug 24, 2016)

smoke665 said:


> Ysarex said:
> 
> 
> > I saw this other poster looking at what you presented and saying that it was swaying his possible future purchase decision. That's why I jumped in. I was concerned that he was being potentially misled with potential costly consequence.
> ...



I didn't say you were, I was just being careful -- all good.

Joe


----------

