[osv]

wide open sharpness is good for shooting star fields at night, and sports in poor lighting conditions, but it won't help when you need to stop down to get dof... macro for instance.

i see your point.

[Topsy]

You mean wide open? Or stopped down?

The people I know that bought old glass (not many at all) went that route due to affordability or lens characteristics.
I don't know if they wanted sharp corners wide open or not, but I'd assume that it wasn't very important for them, not many affordable old lenses I can think of tick that box.

I for one do enjoy sharp edges stopped down, and would assume that others do to. I should've made that clear earlier.

[John Poirier]

Indeed there are many applications requiring corner to corner sharpness. Absolutely.

But at wide open aperture??

I think that's where people are getting confused in the endless discussion about corner sharpness - when wide open!

Correct. Part of the confusion arises from people with limited knowledge, operating on experience with perhaps one fast lens, with expectations created by inaccurate online claims about some lenses being sharp across the frame wide open. I subscribe to the view that corner sharpness when shooting wide open is largely unattainable and usually irrelevant.

What it boils down to is chosing the right tools and techniques for the job. It's just that some people have trouble understanding that photography is a very diverse field with a multitude of jobs.

If people get their jollies shooting wide open, that's great. However, a few assume that the photographic world revolves around that particular technique. It gets a bit tiresome after a while.

[KDAFA]

wide open sharpness is good for shooting star fields at night, and sports in poor lighting conditions, but it won't help when you need to stop down to get dof... macro for instance.

i see your point.

In fact I listed astrophotography as perhaps one of the few cases requiring good corner sharpness wide open.

As for sports, often we're using a longish telephoto focal length for that, and indeed it might be wide open if in low light; together these two factors make for very shallow DOF. Given that we're often targeting at a particular player(s), plus taking into account the shallow DOF, it means the background would be blurred anyhow (we see this very commonly in the photos in the sports section of the newspapers). Again, no need/relevance for sharp corners in this application.

---------- Post added 03-09-16 at 11:41 AM ----------

I don't know if they wanted sharp corners wide open or not, but I'd assume that it wasn't very important for them, not many affordable old lenses I can think of tick that box.

The point is, regardless old lens or new, regardless Brand A or Brand B, reduced sharpness in the corners (when wide open or near to wide open) is a common characteristic. And it improves upon stopping down.

That's why I say it's an endless discussion over a natural characteristic of lenses, and asking for sharpness in corners wide open is neither realistic not necessary/relevant in almost any real life photographic application.

---------- Post added 03-09-16 at 11:47 AM ----------

...part of the confusion arises from ... expectations created by inaccurate online claims about some lenses being sharp across the frame wide open. I subscribe to the view that corner sharpness when shooting wide open is largely unattainable and usually irrelevant.

Agreed.

Trust that Pentax Forums can to some extent help to shed light on this issue, and clarify it for many people.

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Last edited by KDAFA; 03-08-2016 at 09:04 PM.

[osv]

In fact I listed astrophotography as perhaps one of the few cases requiring good corner sharpness wide open.

perhaps? well, cell phone pics are good enough for most people.

As for sports, often we're using a longish telephoto focal length for that, and indeed it might be wide open if in low light; together these two factors make for very shallow DOF. Given that we're often targeting at a particular player(s), plus taking into account the shallow DOF, it means the background would be blurred anyhow (we see this very commonly in the photos in the sports section of the newspapers). Again, no need/relevance for sharp corners in this application.

i needed a fast lens that was sharp across the field wide open for this motorsports situation, and the old vivitar 28/2 in this shot didn't cut the mustard at f/2.8... the track photog was shooting canon ff, 15mm ultra wide zoom wide open... we both had to revert to shooting parallel to the side of the vehicle, because we didn't have enough dof wide open to cover the car from an angle, like we normally would in good lighting conditions, see the second shot 28mm at f/8, with fill flash.

if i'm shooting landscapes at dusk/dawn, i want a fast lens that's sharp to the corners wide open, because it'll also be cleaner at other wider apertures... depending on the focal length, distance to the foreground object, etc., the goal is to run the widest aperture possible, because that allows for the lowest iso settings.

[GeneV]

Maybe yes, maybe no. Before I was willing to move to digital, I wanted to know that it would deliver detail at least as sharp as I had been getting from film, so I sent some of my old Kodachrome 25 slides to a pro to have them scanned. He returned 3000 x 2000 {just under 6MP!} scans to me. Our computer was in what we called "the library" at the time, so I set up my slide projector and screen in there, and compared scans to slides. I had purposefully chosen slides with tiny detail - for example from an annual New Year party a librarian friend of ours used to throw {lots of books around}. Much to my surprise, even those 6MP scans included every detail I could find on the slides - in the center of the image as well as in the corners. Based on that experience, I decided that I would move to digital once a 6MP camera came within my budget,.

My scanner is a 4000dpi Nikon Coolscan 9000 ED, and my Kodachrome scans for 35mm are approx. 5400 x 3600, or 20mp. I played with several resolutins, but settled on that max resolution, because I was still getting more detail from the K25 slide at resolutions well above 6mp. I found it is hard to compare what one sees with on a slide with a loupe to the way we observe detail when we zoom in on scan on a screen. I felt the same way when I made a large Ciba print of a sharp slide, which always seemed to show more detail than a projector or a loupe.

---------- Post added 03-09-16 at 01:12 AM ----------

Yet, despite its reputation for fine grain, Kodachrome was only average in detail capture when compared to the better B&W emulsions. The bar for film photography was set very high even back in the day.


Steve

Agfapan 25 was a true thing of beauty,capable of showing every bit of resolution from a lens on a 16x20 or bigger. I would say those prints were as demanding on the lens and technique than the way we actually use most digital images today,

[KDAFA]

... the old vivitar 28/2 in this shot didn't cut the mustard at f/2.8... the track photog was shooting canon ff, 15mm ultra wide zoom wide open... we both had to revert to shooting parallel to the side of the vehicle, because we didn't have enough dof wide open to cover the car from an angle...

Thanks for sharing the car photos. Not sure if I'm understanding the situation correctly, but looking at the night shot, it does seem to me that the problem arises from somewhat insufficient DOF, which is not surprising since the aperture was stopped down to f2.8 only. In which case, no matter how sharp a lens may be at the corners, that couldn't solve the particular problem here, because those parts of the picture that "don't appear sharp" are in fact slightly out of focus, due to the insufficient DOF as mentioned, and a sharp lens still can't compensate for "out of focus". Perhaps another approach might have been to stop down to f4 or f5, and run the ISO higher. Noisier yes, but hopefully it can be cleaned up in PP, but at least every important part of the picture is within DOF and would appear sharper.

---------- Post added 03-09-16 at 07:11 PM ----------

if i'm shooting landscapes at dusk/dawn, i want a fast lens that's sharp to the corners wide open, because it'll also be cleaner at other wider apertures... depending on the focal length, distance to the foreground object, etc., the goal is to run the widest aperture possible, because that allows for the lowest iso settings.

Yes, but I presume here you mean shooting handheld? Another approach would be to use a tripod, stop down for good DOF to ensure all parts appear sharp, and then choose a slow shutter speed, to keep the ISO down.

[GeneV]

Thanks for sharing the car photos. Not sure if I'm understanding the situation correctly, but looking at the night shot, it does seem to me that the problem arises from somewhat insufficient DOF, which is not surprising since the aperture was stopped down to f2.8 only. In which case, no matter how sharp a lens may be at the corners, that couldn't solve the particular problem here, because those parts of the picture that "don't appear sharp" are in fact slightly out of focus, due to the insufficient DOF as mentioned, and a sharp lens still can't compensate for "out of focus". Perhaps another approach might have been to stop down to f4 or f5, and run the ISO higher. Noisier yes, but hopefully it can be cleaned up in PP, but at least every important part of the picture is within DOF and would appear sharper.

One big advantage I have seen to the 36mp Sony sensor is the ability to shoot at higher ISO. It is not the high-ISO monster of Sony's line, but you can still shoot a stop or two higher than with the K3. I did not expect this from this sensor, but it works out that way if you are using the entire frame. The better the high ISO performance of sensors gets, the more limited the need for a large aperture.

We touched on this in another part of the forum, but at some point, the advances in PP should cause everyone to think a bit outside the box about lenses for digital work. Is a lens with beautiful corner sharpness as critical for landscapes when you can easily stitch together shots which place the important areas in the sharpest field of the lens? (not that there aren't other uses for uniform sharpness) Is a view camera or a lens which performs well at a tiny aperture necessary for product photography with the state of focus stacking software? I watched a world renowned pro architectural photographer work indoors last week, and while he still had a tilt-shift lens along, he was taking most shots with another lens and using transformations on the spot from Lightroom to get the final result to show the art director and client. PP is a fact of life, now. A decade from now, advances in digital lenses could be that they perform in ways which would have been unacceptable on film.

[KDAFA]

One big advantage I have seen to the 36mp Sony sensor is the ability to shoot at higher ISO. It is not the high-ISO monster of Sony's line, but you can still shoot a stop or two higher than with the K3. I did not expect this from this sensor, but it works out that way if you are using the entire frame. The better the high ISO performance of sensors gets, the more limited the need for a large aperture.

We touched on this in another part of the forum, but at some point, the advances in PP should cause everyone to think a bit outside the box about lenses for digital work. Is a lens with beautiful corner sharpness as critical for landscapes when you can easily stitch together shots which place the important areas in the sharpest field of the lens? (not that there aren't other uses for uniform sharpness) Is a view camera or a lens which performs well at a tiny aperture necessary for product photography with the state of focus stacking software? I watched a world renowned pro architectural photographer work indoors last week, and while he still had a tilt-shift lens along, he was taking most shots with another lens and using transformations on the spot from Lightroom to get the final result to show the art director and client. PP is a fact of life, now. A decade from now, advances in digital lenses could be that they perform in ways which would have been unacceptable on film.

There's no doubt advances in digital PP are challenging ways of thinking and working in photography.

[GeneV]

There's no doubt advances in digital PP are challenging ways of thinking and working in photography.

Just thinking that there is an argument to be made that high quality film can be more demanding of a lens than 36mp digital.

[osv]

Thanks for sharing the car photos. Not sure if I'm understanding the situation correctly, but looking at the night shot, it does seem to me that the problem arises from somewhat insufficient DOF, which is not surprising since the aperture was stopped down to f2.8 only. In which case, no matter how sharp a lens may be at the corners, that couldn't solve the particular problem here, because those parts of the picture that "don't appear sharp" are in fact slightly out of focus, due to the insufficient DOF as mentioned, and a sharp lens still can't compensate for "out of focus". Perhaps another approach might have been to stop down to f4 or f5, and run the ISO higher. Noisier yes, but hopefully it can be cleaned up in PP, but at least every important part of the picture is within DOF and would appear sharper.

you could be right about the dof, if i wasn't perfectly parallel to the side of the car... that could be the case, it bugs me because the area around the rear tire is sharper than the front fender/tire area, however the front of the car has more movement... i was already at iso10,000, and i dropped the shutter to maybe 1/2000th(?), and even tried to pan on some of the shots, to make up for the slower shutter.

i've tested that lens at all apertures, so i know that it doesn't deliver at wide apertures on 36mp... by comparison, guy mancuso tested the batis 25mm prime on the a7rii, look at the corners: Sony A7RII/ Batis 25mm , Batis 85mm and Sony 35mm 1.4 System Tests

landscapes at f/4 are doable there... when there is wind blowing leaves around, birds in the sky, people/animals in the shot, you may want to try f/4.

here is a possible example of that... the front end of the white truck is probably 10' off of the ground. he's flying off of the top of a steep hill, so i had to use a fast shutter... if it had been dusk, the ability to open the aperture and still retain pq in the corners would have been very helpful, i could have kept the fast shutter with minimal iso noise... lens was an m35/2.8.

i would have much rather shot it later in the day anyway, because the sun at noon on the sand doesn't leave much in the way of shadows, the flat lighting just kills this photo... that's actually a big hill, but there isn't any sense of depth to the shot... i could have maybe opened the aperture up, but i was wondering if i'd lose the resolution on the mountain range in back.

[reh321]

Usually, pictures I take have a central interest that is in the middle two-thirds of the picture. I want that to be in focus. The rest of the image provides context, so I don't demand needle-sharpness there. I probably should also mention that I tend to avoid extremes of the lens - I really do prefer apertures like f/5.6 and f/8. But that is just me. If you're dissatisfied with a lens, just let me know ... I promise to drive a good bargain {for me}

[KDAFA]

you could be right about the dof, if i wasn't perfectly parallel to the side of the car...

... i was already at iso10,000, and i dropped the shutter to maybe 1/2000th(?), and even tried to pan on some of the shots, to make up for the slower shutter.

I could be wrong here, but it seems to me that EVEN IF you had been perfectly parallel to the car, even then, the straight-line distance from your lens to the car's middle is different than the straight line distance from your lens to the car's front fender/rear fender (simple triangular geometry).

Depending how far you were standing from the subject, this difference in distance I suspect may be enough to cause the fender portions to be slightly out of focus with respect to the car centre, simply because of the somewhat inadequate DOF at f2.8.

Put another way, the centre of the car may well be in accurate focus, (which it is in that picture), but the front and rear ends of the car, being quite a large subject, may already be drifting slightly out of focus, all the more if you were standing quite close by snapping the shot. And I think the only way out is to stop down more, maybe f4 or 5, to increase DOF. But I know this causes ISO noise.....

Also, even with some other lens, which is sharper in the corners when wide open, it still can't solve this problem, because sharpness can't overcome out of focus; hence the need to stop down to obtain enough DOF, and as a bonus, also get improved corner sharpness.

This was one of the points I was making earlier - when a lens is wide open or near wide open, the DOF is going to be small, and it's going to be really, really hard to get any significantly large portion of the picture to be in focus, no matter how sharp or not sharp the lens may be, because the DOF is shallow. So sharpness in the corners wide open just isn't relevant in most cases I can think of, because the DOF is going to be so shallow.

Wow, didn't realise it was 1/2000 second. I'm not experienced capturing motion at such high shutter speeds. Was 1/2000 needed? Because for sure that would run your ISO way up.

Love the fill flash in the second shot...

[bobbotron]

It's the old "sensors out resolve lenses" argument rehashed for the 18 bazillianth time. Under that theory, new increase in sensor technology won't produce any more resolution because the old sensor already had maxed out the lens. The only problem with this theory, is, it's never happened. Old lenses keep producing higher res, on newer more compact sensors in a relatively linear fashion.

The corollary to this line of thinking is lenses are so closely matched to seniors that a TC won't do any good. You'll get the same subject resolution if you just use the lens by itself and increase the size with software.

Both these notions have been repeatedly dismissed by actual real world testing. IN fact Imaging Resources tested a bunch of lenses on the 7000 and 7100 to see if lenses started failing under the stress of the more compact sensor. They found the exact opposite. The cheaper lenses, often gained about 60% resolution while the best lenses gained about 20%. SO in fact the opposite to the "common wisdom" is true. Your bad lenses area actually more likely to benefit from increased pixel density than your sharpest lenses.

So to summarize...
This whole thought process has not one bit of data to support it. Even the average lens can benefit from a tighter pixel density, and even more than the good ones.

To date no one has come up with any kind of theory to explain why this would be true, so the "the sensor will out resolve your lens" nonsense continues to be repeated.

I have noticed that tiny camera shake is way more apparent with the k3 than a camera with a smaller sensor. Darn thing doesn't cut you any breaks if you're shaky. (Nor should it!) Using a flash or tripod really shows how sharp your lenses can be with it.

[osv]

I could be wrong here, but it seems to me that EVEN IF you had been perfectly parallel to the car, even then, the straight-line distance from your lens to the car's middle is different than the straight line distance from your lens to the car's front fender/rear fender (simple triangular geometry).

true, that's field curvature, and unfortunately most lenses have too much of it: Tim Ashley Photography | Field Curvature - a Layman's Guide (or How to Focus a 'Tricky' Lens)

more dof does cover it up, but if you can start off with a flat field lens like that batis 25mm appears to be, or with the legacy glass, a canon fdn24/2.8, you'll be able to run wider apertures and have a bigger margin of error for focusing... i think that shot that reh posted is difficult, because the right side of the train is further away, the opposite direction of field curvature, but we don't care so much because it's not integral to the photo, and in fact softness there may even be preferable.

people usually shoot those cars further down the track, with longer lens, and they run slower shutters, i just can't seem to pull it off from that close angle... when i went to 36mp, i could run it at 1/3200th, everything in the frame was sharp, but sometimes the engine was soft due to vibration... overall, i'd much rather shoot it stopped down, like you said, don't need the sharp corners.

here is a good example of not needing sharp corners for sports, it's basketball shot from the floor, 85/1.4 at f/1.4(!!) on ff: Basketball: Sport and Action Photography Forum: Digital Photography Review

he probably had to shoot a thousand pics to get those winners, but hey, if that's what it takes!