PDA

View Full Version : Schneider Super-Angulon 90mm/f8 - potential issues



uncommonfaces
6-Apr-2019, 12:47
I'm just testing one of these and have a couple of concerns.

1. The Copal shutter aperture blades appear to be in contact with the glass on the rear cell. The Schneider spec sheet for the lens has 'Overall length' at 74.9 which is dead on, but I don't know how to measure 'Lens seat to lens rear' in attached. This is in a Copal 0 shutter (it also has an 8 to 64 scale rather than 8 to 45 as per spec sheet). Wondering if anyone can corroborate blades touching (or very, very close to) glass?

189721

2. I've only made one test image so far (ran out of film until next pay day), but the left third of frame is slightly fuzzy. There is also a smaller local area mid right that has similar fuzziness, while all around it sharper. Made extra sure everything on the camera was zeroed, so definitely not swing related. I'm wondering if decentering or rear cell related if #1 seems weird to others?


Other facts:

- Shot at f32
- Scanned on V800 with standard holder, all focus notches set the same
- I make this mantelpiece test neg/scan with all the lenses I've tried or own and haven't seen local softness until this one

Bob Salomon
6-Apr-2019, 13:03
F32 puts you in diffraction. Test at 16 or 22. How do you know that you are at 32 since your shutter has the wrong aperture scale?

uncommonfaces
6-Apr-2019, 13:30
Yeah I'm aware diffraction is just kicking in and of course I can see affects of diffraction further stopped down, but general softness is different to uniformity of sharpness. At the f8 marker the diaphragm is exactly at edges of lens opening. I believe f stop spacing is same across scales? So this scale is only wrong in so far as it should just stop at 45? - https://www.largeformatphotography.info/forum/showthread.php?150232-Identifying-correct-rear-element-and-shutter-for-lens&p=1480021&viewfull=1#post1480021

Bob Salomon
6-Apr-2019, 13:35
Yeah I'm aware diffraction is just kicking in and of course I can see affects of diffraction further stopped down, but general softness is different to uniformity of sharpness. At the f8 marker the diaphragm is exactly at edges of lens opening. I believe f stop spacing is same across scales? So this scale is only wrong in so far as it should just stop at 45? - https://www.largeformatphotography.info/forum/showthread.php?150232-Identifying-correct-rear-element-and-shutter-for-lens&p=1480021&viewfull=1#post1480021

Call Schneider and get a set of proper scales, that will take the guess work out of what you are trying to do.

uncommonfaces
6-Apr-2019, 14:17
I've just measured and all is spot on across apertures.

In relation to the soft left portion of frame, might the missing paint in the attached be the issue? This is rear element of front cell. At f8, the diaphragm is actually obscuring the missing paint (as it's in line with the outside of the rest of that black rim), but wondering.

189736

Dan Fromm
6-Apr-2019, 14:39
Is the shutter a Copal Press (top speed 1/125) or a cock-and-shoot (top speed 1/500)?

uncommonfaces
6-Apr-2019, 14:49
Is the shutter a Copal Press (top speed 1/125) or a cock-and-shoot (top speed 1/500)?

Cock and shoot, 500.

Dan Fromm
6-Apr-2019, 15:41
Then the front of the rear cell should clear aperture and shutter blades. If there's contact between aperture blades and the front of rear cell, there will be scratching.

Everything in the image you posted is soft. There's no fine detail in the left side so detecting softness there is very difficult. Go shoot a nice brick wall. Make sure the back of the camera and the lensboard are parallel with the wall and focus carefully.

uncommonfaces
6-Apr-2019, 16:29
Then the front of the rear cell should clear aperture and shutter blades. If there's contact between aperture blades and the front of rear cell, there will be scratching.

Everything in the image you posted is soft. There's no fine detail in the left side so detecting softness there is very difficult. Go shoot a nice brick wall. Make sure the back of the camera and the lensboard are parallel with the wall and focus carefully.

Yes makes sense there should be clearance really. Thanks.

Sorry, full res image here - https://drive.google.com/open?id=1kp007ZzXe6gr1mUjd9Iyo9uaucEanxwu

(Focus point is the ruler, f32. I made the same image a few days ago testing a 125mm, same focus point and aperture, and the left from carpet to wall is sharp, so I'm pretty certain it's not just insufficient DoF with this particular lens). I've also just made another scan to make sure all was flat and same softness, same places.

Bob Salomon
6-Apr-2019, 16:47
Yes makes sense there should be clearance really. Thanks.

Sorry, full res image here - https://drive.google.com/open?id=1kp007ZzXe6gr1mUjd9Iyo9uaucEanxwu

(Focus point is the ruler, f32. I made the same image a few days ago testing a 125mm, same focus point and aperture, and the left from carpet to wall is sharp, so I'm pretty certain it's not just insufficient DoF with this particular lens). I've also just made another scan to make sure all was flat and same softness, same places.

You do know that for most work DOF runs 1/3rd towards the camera from the point focused on to 2/3rds away from that point?

uncommonfaces
6-Apr-2019, 17:00
You do know that for most work DOF runs 1/3rd towards the camera from the point focused on to 2/3rds away from that point?

Yes I do. In which case, the back wall/picture frame on the left should be sharper than the cushions in the lower right? The cushions are further from the plane of focus than the wall but sharper. Actually though it's the DVDs which are closer to the plane which are weirdly soft.

Huub
7-Apr-2019, 00:47
At f32 your dept of focus should be plenty enough to make almost everything in this picture sharp. What i find weird is that you are indicating certain area's of the picture that are possibly less sharp then others. I would expect that with a faulty lens unshaprness would either be on one side of the picture or could be seen in some of the corners, especially when using maximum shift on a lens like this, but not in a few specific areas in a picture. My guess is that you are seeing the effects of diffraction, manifesting itself in the areas that show plenty of detail. Take the earlier advice and shoot a nice brickwall or something flat and stop down to f11 or f16. When unsharpness appears in the same areas again, then it might be your lens indeed, but it could also be that the problem comes from film flatness issues or something complete else.

ic-racer
7-Apr-2019, 05:18
You might try testing the lens wide open, if you want to bring out defects, rather than hide them.

In my experience, without some kind of ISO standard testing laboratory, you have no comparison standard. The best way I have identified lens defects is when I obtained two samples of the same lens and tested them side by side. For example I had two 90 Topcors. One had 2mm edge separation. The lens with separation was perfectly acceptable, but in side-by-side comparison, the non-affected lens was ever so slightly sharper in the corners of the negatives.

189764

uncommonfaces
7-Apr-2019, 06:29
Take the earlier advice and shoot a nice brickwall or something flat and stop down to f11 or f16. When unsharpness appears in the same areas again, then it might be your lens indeed, but it could also be that the problem comes from film flatness issues or something complete else.

I will do yes. And film flatness certainly a consideration. I'll try another holder and fresh box of film to rule that out.

What do people think to the chipped paint on the rear of front cell however? This area was on the same side of the image as the left block of fuzziness I've indicated.

Paul Ron
7-Apr-2019, 10:26
is it possable the spacing between front n rear cells needs some adjusting with shims? the spacing may be the problem.

Jac@stafford.net
7-Apr-2019, 11:06
When you find deviations in focus it is always necessary to eliminate problems top-down. For example maybe the film was not loaded under one side of the film holder's retention rails.

alan_b
13-Apr-2019, 10:39
Also try comparing with the lens board rotated 180˚.

Dan Fromm
13-Apr-2019, 12:01
I will do yes. And film flatness certainly a consideration. I'll try another holder and fresh box of film to rule that out.

What do people think to the chipped paint on the rear of front cell however? This area was on the same side of the image as the left block of fuzziness I've indicated.

Show us the chipped paint. The only lens pictures I can find in this discussion were posted by ic-racer.

Bob Salomon
13-Apr-2019, 13:46
At f32 your dept of focus should be plenty enough to make almost everything in this picture sharp. What i find weird is that you are indicating certain area's of the picture that are possibly less sharp then others. I would expect that with a faulty lens unshaprness would either be on one side of the picture or could be seen in some of the corners, especially when using maximum shift on a lens like this, but not in a few specific areas in a picture. My guess is that you are seeing the effects of diffraction, manifesting itself in the areas that show plenty of detail. Take the earlier advice and shoot a nice brickwall or something flat and stop down to f11 or f16. When unsharpness appears in the same areas again, then it might be your lens indeed, but it could also be that the problem comes from film flatness issues or something complete else.


You mean depth of field? That is the area in apparently sharp focus in front of and behind the point focused on. The wider the lens the greater the depth of field is.

Or do you mean depth of focus, that is the area behind the lens that the image plane must lie on. The wider the lens the narrower the depth of focus.