A look at lens sharpness

[fmw]

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?

No reason. How silly of me to want to give information to beginners.

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?

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]

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.

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

 

[Ysarex]

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.

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

They're camera generated JPEGs.

Joe

 

[robbins.photo]

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?

No reason. How silly of me to want to give information to beginners.

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?

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

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]

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.

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

They're camera generated JPEGs.

Joe

And what causes them to invalidate the images?

 

[fmw]

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?

No reason. How silly of me to want to give information to beginners.

No purpose. I'll try to delete it.

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?

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

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?

 

[jcdeboever]

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.

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:

View attachment 126448

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.

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.

Excellent, informative, and useful.

 

[jcdeboever]

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?

No reason. How silly of me to want to give information to beginners.

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?

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

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

 

[KmH]

Tutorials – Sharpness

 

[Overread]

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]

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.

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

They're camera generated JPEGs.

Joe

And what causes them to invalidate the images?

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]

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

 

[robbins.photo]

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]

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]

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