10x8 film flatness

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Tom Stanworth

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Hi,

being new to 10x8 I shot a test shot on a new (used 159 Wolly) at f22. The back was tilted forwards a fair bit along with the base/lens plane etc (shot from 1st floor window opinting down a bit). I figured that with short lenses, film flatness would be particularly important so I thought it would tell me what sort of an issue it is likely to be. Result?

Sharp edges and progressively softer towards centre (very noticeably soft). I supected with big film softness might be the result as it is going to sag.

Is this what one should expect?
Is it a no-no to have the film anything but vertical and preferably slightly leaning back to ensure best flatness. Tilting back should be easy enough in many landscape scenarios or at least vertical.

Anyone with more experience who can comment on this subject?

As a preliminary comment on teh Wolly 159 12.5, it seemed a decent performer (edges at least!). Not a modern lens, but should look fine considering low enlargement factor (even for a 30" print or so). I will shoot another frame tomorrow with the back vertical to see what it is really like!)

Tom
 

George Losse

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Tom,

Not all holders are created equal and not all films will handle this the same.
This can be a problem films with thin film base. You didn't mention what the film was you were shooting.

I've never had this problem but most of my subjects have been in front of me. I don't point the camera down to often, just worked out that way.

There are holders that pull the film tight (I don't remember which).
 

Donald Miller

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Tom Stanworth said:
Hi,

being new to 10x8 I shot a test shot on a new (used 159 Wolly) at f22. The back was tilted forwards a fair bit along with the base/lens plane etc (shot from 1st floor window opinting down a bit). I figured that with short lenses, film flatness would be particularly important so I thought it would tell me what sort of an issue it is likely to be. Result?

Sharp edges and progressively softer towards centre (very noticeably soft). I supected with big film softness might be the result as it is going to sag.

Is this what one should expect?
Is it a no-no to have the film anything but vertical and preferably slightly leaning back to ensure best flatness. Tilting back should be easy enough in many landscape scenarios or at least vertical.

Anyone with more experience who can comment on this subject?

As a preliminary comment on teh Wolly 159 12.5, it seemed a decent performer (edges at least!). Not a modern lens, but should look fine considering low enlargement factor (even for a 30" print or so). I will shoot another frame tomorrow with the back vertical to see what it is really like!)

Tom

Tom, Another factor that may be involved is the orientation of the object photographed in relation to the film plane. For instance if you were photographing a utility pole and the camera was pointing downward to the pole then the back must be parallel to the pole or you will have out of focus on portions of the image. In your description this could have accounted for unsharpness.

Additionally if you were photographing a horizontal scene in your example with the camera base pointing downward, the back should have been effectively tilted backward since the effect of a tilting back is counter that of a tilting lens.

I would be more inclined to question the camera movements then I would film sag. Additionally F22 is not stopping down very much with 8X10. One can easily stop down to F45 without diffraction becoming a factor. F64 is not out of reason when contact printing 8X10
 

roteague

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Donald Miller said:
I would be more inclined to question the camera movements then I would film sag.

My thoughts as well. Try looking at Steve Simmons book on the View Camera, he has a good section on just this subject.
 
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Tom Stanworth said:
Sharp edges and progressively softer towards centre (very noticeably soft). I supected with big film softness might be the result as it is going to sag.
Tom, as others have remarked, the appropriate camera movement looking down onto a street from a high viewpoint would be to tilt the camera back backwards (probably not enough coverage with your lens to tilt the lens forwards very much). However, use of incorrect amounts of tilt would result in a horizontal band of sharpness across the neg and progressive unsharpness away from this. Do I understand it correctly that ALL the edges are sharp in your neg, with an unsharp center? It is not impossible for older wide-angle lenses to exhibit focus shift on stopping down, and an f12.5 lens is rather dim to focus anyhow, but I would suggest spending some time under your focusing cloth with a loupe with the same camera set-up you used before, focusing on the center and (after your eyes have acclimatized to the dark) then observing any changes in central sharpness as you stop down to f22, then f32 and f45. If center and edge are not both in focus at f12.5 (which is likely) you may get the best results with this lens (which I don't know) by focusing "off" by a small amount and then closing down to f32 or smaller. If after close scrutiny the image appears accceptably sharp on the screen but not on the film, then there may be a film flatness problem. You may need to sacrifice one sheet of film by placing a holder in the camera, pulling the sheath, leaving it for 5 minutes and then taking the camera back off (without tilting it) and looking at the film in daylight.

Also check the specification of the film you are using if not Ilford/Kodak. The usual base thickness for sheet film is 7/1000" or 0.18 mm, anything thinner than this could conceivably also cause problems.

Regards,

David
 
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Tom Stanworth

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I do not think it is a movements issue as it was sharp on the GG! f22 was fine as closest object was about 10m and furthest about 100, focus beng achived through light front tilt and some rear. The camera back was tilted backwards to an extent, but not to vertical. There were no vertical elements of significance in the image, so I did not need a vertical back and lens plane. There was also not a horizontal band of sharpness. It was sharp everywhere around the film edges top, bottom and sides, just not the central portion (the reverse of what would happen with a lens wide open with insufficient coverage). Deterioration incresed towards the central 'area'. It was a circular area of softness and therefore not associated with movements (objects above, below, left and right were sharper than the middle). I will reshoot and find out.....I hope it is not a lens issue. I doubt it.

I used FP4 plus in fidelity holders. I personally suspect that the back was far enough forwards to cause sagging.
 
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Just to be quite clear - have you checked the image on the GG at TAKING aperture (e.g. f32)? Have you ascertained that the focus is not shifting as you stop down (i.e. the focus is OK at f12.5 and also at the taking aperture)? Stop-down focus shift is an odd phenomenon of which you may not be aware if you have only used "modern" lenses, where definition and circle of sharpness increase as you stop down, but focus stays the same. Have you examined a sheet of film in a holder after it has been in a tilted-forward position for a few minutes (to see if it sags)?
If you have tried all these things, the only way to get a sharp neg. with your set-up may be to defocus the camera back by moving it back say 2 mm from the apparent best-focus position to what is effectively a compromise position between the flat edges of the film and the sagging center and then shooting at a really small stop, f45 or 64.

Regards,

David
 
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Tom Stanworth

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I will try a sheet in the holders to look for sag. If there was focus shift, it should affect the whole image. I dont see how if there was shift it would leave the edges sharp (whch were sharp on GG) I focussed oepn but did not recheck at working aperture. Not something I have ever needed to do before......will check visually for focus shift. I cannot see that I would ever need the back tilted fwds in preactice, but seeing as I did on this occassion, it certainly has given ise to some questions!

Tom
 

Deckled Edge

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Is this even an issue?

I have over 2000 negatives, made with every sheet film from 2-1/4 x 3-1/4 up to 11x14, and recently, 7x17. I don't have one that suffers from lack of film flatness in the holders. I agree with George, that it has never been a problem. I have shot with T Max (all flavors) HP5, Delta, Tri X, Super XX, PL100, and J&C 200. I have holders that were possibly owned by Crimean War correspondents. My holders are often loaded months in advance and stored upright. I shoot in desert heat, and snowy chill.
Film flatness concerns SHOULD worry us all, but in truth, the technology of the late 19th Century seems to have licked the problem. True, you could get a bent holder and load it with Kodak Lite or some gossamer film. In practice, though, we don't shoot at f2.8, and the DOF that brings in faraway planes also handles the sub-millimeter differences at the film plane.
The only thing that distinguishes my 2000 negatives is that none of them were shot looking down. I suspect all the shots were made with the back vertical or with rear tilt. For my next series on well bottoms I will use the two-sided tape trick and lay in a case of adhesive remover for use in total darkness to remove the residue.
 
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Tom Stanworth

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Deckled Edge said:
.
The only thing that distinguishes my 2000 negatives is that none of them were shot looking down. I suspect all the shots were made with the back vertical or with rear tilt. .

But this surely could make the world of difference! I played with a sheet of dev'd film in a holder and the results were interesting.

If held vertical, the film was flat, if held upside down or even at and angle downwards, the film stayed flat for a little while (maybe 10-20 seconds) and than slowly sagged. Tapping ones finger against it revealed just how much sag was there (plenty). Strangely, once returned to the vertical, the 'bow' remained until the holder was rattled to resettle the film. Settled film in the vertical was flat against the metal, unselttled film could be agood 1-2mm proud, if previously at an angle or upside down). bowing was most pronounced towards the centre (as expected) but with a major bias towards the darklide end (I guess as pressure is not exerted as well by the light trap area as by the end flap (where flatness was much better). I have heard of people 'tapping' their 10x8 holder prior to use and now think that there may be a very good reason for this. I would guess that if ones holders are always stored vertically (mine were not incidentlly) this would not be a problem. I suspect therefore that as mine had been stored flat immediately before use (and some time before) AND I shot with the back forwards AND I did not rattle the film flat, that I may have generated the worst possible circumstances for film flatness. Combined with a relatively short focal length (159mm) and an aperture of f22 (rather than f32/45), this might have mattered. Upon further examination of teh neg, there is the same worsening of flatness towards the insertion end of teh holder, which makes me all but certain that this is the cause. I also tried for focus shift with the lens (and my 159 12.5 Wolly opens up to about F9 as screw removed) there was no focus shift compared to f22/32.

Tom

Tom
 
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There's one thing about photography - you never stop learning! Like "Deckled Edge", I would not have believed that film sag could occur to this degree. Although I have not shot many 8x10s recently, despite having 2 cameras, I worked in a studio for 2 years 1970 - 1972 and shot a dozen or more 8x10s every day, using relatively new Fidelity holders, older Kodak holders and also some very old wooden ones whose name I forget, and I never encountered this problem. This is why I was going on so much about testing for focus shift! On the other hand, I do instinctively stored loaded unexposed holders vertically.
Anyhow, it sounds as if you have the problem licked with vertical storage of holders plus a tap before insertion into the camera!

Regards,

David

PS: Just one final thought - you are probably doing this anyway, but are you 100% certain that when you load the film, it inserts fully and the leading edge goes under the small lip inside the film holder at the "top" (i.e. the end where the sheath goes in)?
 
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Tom Stanworth

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David,

Film loaded all the way in, for sure. I will shoot 2 frames today, one where I am taking basic precautions for flatness and another to try to recreate what happened. I figured that because shorter lenses have a more critical flange to film distance for correct focus, sag would affect short lenses far more than long ones. I shot a sinilar test exposure with my 300 F9 geronar, tho pointed less downwards and had no problem. Perhaps the lesser downwards angle and the more forgiving longer lens (at f32) meant there was no problem. I know from experience with my 47mm and 65 on 5x4 that being a tiny bit out on focus is not recoverable thru DOF as correct focus to no focus can be 1 or 2 mm. It would be less at 159mm, but still a possible explanation. Still, where the neg from the 159 wolly was sharp, it was surprisingly so for such a cheap (relative) old lens. I just hope it covers well enough for enlargement (not currently contact printing)...will soon see!

Tom
 
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