Schneider Super-Angulon 90mm/f8 - potential issues

[uncommonfaces]

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?



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]

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]

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.i...=1#post1480021

[Bob Salomon]

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.i...=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]

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.

[Dan Fromm]

Is the shutter a Copal Press (top speed 1/125) or a cock-and-shoot (top speed 1/500)?

[uncommonfaces]

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]

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]

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=1kp...Iyo9uaucEanxwu

(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]

Yes makes sense there should be clearance really. Thanks.

Sorry, full res image here - https://drive.google.com/open?id=1kp...Iyo9uaucEanxwu

(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?