2/35mm asph corner sharpness?

[schn€id€r]

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Hello,

 

the following picture was shot with an MP and a 35mm summicron asph. probably at f: 5.6 or 8.

 

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There seems to be a considerably blur in the upper right corner, in detail here:

 

 

I find this effect with many sorts of films quite constantly in such situations with this lens (not with others, which seems to exclude the scanner as a source of this effect). It is visible in all corners, if there are detailed structures, such as in the example.

 

Is this a normal phenomenon with this lens, in your experience, or do you think it somehow out of an acceptable range? In other respects, I like this lens very much, but this unsharpness in the corners is sort of irritating me.

 

Thank you for your advice, and best wishes for 2010

 

Michael

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[Ivar B]

No, this is not the way it should be. Your lens also shows a large amount of flare, and I do not experience this with my version of the lens. If you did not use a greasy filter or there was some other problem when you made this exposure, you should have the lens looked after by Leica.

[el.nino]

this was shot directly in the sun, wasn't it?

that would explain the blur.

do you have any photo that was not shot against the light?

you might want to take a picture of a brick-wall to test the corner-sharpness.

[Ivar B]

el.nino has a point, but a lens of this calibre should show much less flare. It is a good test to see if a lens is cabable of drawing leaves in front of a bright sky properly, and here it looks like there may be a problem although having access to one photo clearly is insufficient.

[batmobile]

could be film halation too, but gross localised overexposure can make this happen with any lens. It also looks like it was either overexposed or you used a filter. Can you explain all the kit used to help? I have a suspicion this is not a lens fault.

[schn€id€r]

Hello,

thank you very much for your appraisals. Some additional informations: I used no filters, and this photograph was shot on Neopan400, developed in Emofin (two-bath). There might be overexposure which would explain the flare, though I don't think that there is more flare than should be in this situation (at least much less than my pre-asph. 35 summilux would show). The sky was very bright, although the sun was outside the frame. My point really is just the blur in the corner, perhaps the last one or two millimeters of the frame.

 

There is another picture with the same lens where the sky was very cloudy, but still much brighter than the the twigs and leaves (again no filters, f: 8 or 11, and TriX in ID 11):

 

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As the following detail from the middle shows, the lens handles these contrasts very well, and there is no flare (at least I think so):

 

 

And this detail from the upper right corner shows the blur again, especially in the right half, whereas the left half of this detail still seems o.k.:

 

 

Might this be an effect of "field of curvature", which has not been completely eliminated (not just with my lens, but with the lens design)? I have to say that this effect is less pronounced than on my pre-asph. summilux 35mm, but much more than I expected when buying this lens.

 

Thank you very much again for your help!

 

Best wishes

Michael

[jaapv]

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The quality fall-off of this lens to the corners should be negligible. this is not a very good test shot though. Maybe you could try something less contrasty and more regularly structured?

[schn€id€r]

Thank you all very much so far. jaapv, you are right, these pictures have not been intended as test shots, so I'll look for brick walls or something similar. Another possibility might be insuffient flatness of the film, be it in the camera or the scanner. That will be clarified when some future day a M9 is within financial reach for me.

 

Best wishes

Michael

[batmobile]

Here's my thinking:

 

You are shooting with an exposure such that you retain detail in the shadows against a very bright sky. Even with a two bath you are still likely to be dealing with a massive exposure range. This overexposure of the high values places a heck of a strain on the rentention of shapr detail in the twigs/branches. Try shooting something in more moderate contrast.

 

You are shooting a 400 speed film, which altho one of the finest traditional films there is, offers nowhere near the fine detail of, say Delta100. This would be much more revealing.

 

You have used emofin, which I recall is very soft working re grain and acutance. Again, this makes determination of detail tough as everything goes mushy.

 

I would retest shooting a regular scene with fine detail across from corner to corner. Use a slow film and either a tripod or a speed or 1/250 or so. You can use a brick wall, go stand on a bridge and shoot one strip showing the skyline on the bottom of the frame and another at the top, you can go up a tall building and do the same. Lots of ideas. Then look at the corners vs centre again. Use a regular developer like D76/DDX/Xtol/HC110/Tmax etc. Do not use perceptol, microdol or any sovent developers unless used very dilute as they all mess with the fine detail.

 

There may be a lens issue, but looking at the circumstances of the above, it is possible that a number of factors have all added up to give the effect you are seeing.

[alun]

You say the sun was just out of frame to the right and to me it looks pretty much like one might expect from slight veiling flare and a degree of under-exposure.

[Shootist]

You really need to shoot a flat surface with detail, like a brick wall, with the camera as close to 90° in both the vertical and horizontal plane as you can make it.

 

What you're photographing, showing images of, is at all different distances from the camera and almost impossible to tell just what you were actually focusing on.

 

Also at smaller f/stops you have to deal with diffraction which can also be part of the problem.

Also there is focus shift with every lens ever made causing the lens to change focus point as the lens is stopped down. No RF camera can correct for that shift as it never knows what aperture you are shooting at.

 

That's not to say your copy of this lens is not adjusted correctly but with the images you have posted so far it really is hard to tell.

[schn€id€r]

Thank you all again; that has been very helpful, and I'll to find out more according to the ways suggested above!

 

Best wishes

 

Michael

[schn€id€r]

Hello,

 

for those who are still interested, there are some more definite results of lens testing I’ve been recommended (sorry that it took some time).

 

I compared three 35mm lenses (the pre-aspherical summilux 35mm, the first 8-lens-design of the summicron 35mm, and the current asph. version which seemed to present some problems concerning corner sharpness mentioned above). All pictures were made with tripod, wire release, Acros 100 in Rodinal 1+50, and apertures from f: 4 to f: 16, focus at infinity, resulting in this overall picture:

 

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But I was interested mainly in the corners. The results were quite interesting. To make it more intriguing, let me pose it as a question: Which of the two following pictures (both f-stop 5.6 and focus at infinity) was made, in your opinion, with the 35mm Summicron asph.? (right upper corner of the image above)

 

a)

 

or

 

 

That overall sharpness is not too good is due to downscaling; the originals are fine; but the differences between a) and are, I think, clear enough. I look forward to some guesses!

 

Best wishes

Michael

[Xmas]

You have only posted two results when you are testing three lenses.

 

The pre asph lux at /5.6 should be good in the corners, i.e better than a type I cron, But you need something better then the supplied Leitz hood, or you will get veiling flare, even in this sort of scenery, the asph should be as good as the old lux, donno how you got this difference...

 

Noel

[palec]

Looking at MTF chart the 35mm Summicron ASPH has weaker corners by design which proves Sean Reid test on M8 (I guess on M9 it will be more obvious). But at f/5.6 it should be corrected already and I guess there is something wrong with alignment of the lens/elements - at least I had similar problem with version III Summicron which has been fixed by Will van Manen.

[jaapv]

Palec is quite right. There may be a slight fall-off towards the corners, but it will certainly outperform previous versions. If it does not it should be checked. I will have a look later at mine using the M9. Digital is far more sensitive to such things, so if there is anything it should show up. And any problems with film flatness ( a frequent cause of such problems) will be eliminated.

[adan]

I might point out this previous post of mine: http://www.l-camera-forum.com/leica-forum/customer-forum/112954-normal-35-f-2-asph.html

 

While it deals with point light sources - all photographs are effectively made up of point light sources, and so aberrations will still have some effect in any picture, just not as obvious.

 

The 35 f/2 ASPH is a technical improvement over the previous versions in several ways, but it is not perfect. I swapped mine for a pre-ASPH v.4 (+ a used Canon 5D) for reasons not directly related to corner performance.

[jaapv]

The lens is certainly not perfect in the corners, Andy, but at 5.6 it is pretty good.

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[luigi bertolotti]

If it's the first of your 2 pics that has been taken with the Cron asph, I'd say that your item maybe has some issue; I have it, as well as the two other 35 you quote (Summicron 1st and Summilux un-asph) and made one-to-one comparisions only with M8, but at corners the 35 asph is always definitely the best, at any f stop (even if the Summilux is indeed surprisingly good when closed at 5,6 / 8... but one mounts a Summilux when WANTS to use 1,4... and the old Lux 35 is really so-so when wide open)

[tobey bilek]

Film has to be dead flat in scanners and enlargers.

 

Examine the corners with a 50mm lens reversed to see if the neg is sharp. If soft, then it has a problem.

 

If sharp, you need to find a way to get them flat for the scanner.

 

BTW, all the corners look soft.