filmflatness: glue?greenspun.com : LUSENET : Large format photography : One Thread
I read a lot about lensquality, filmsharpeness etc.. For a sharp picture my main concern at this moment is how to keep the film flat in the filmholder. Should I cut the strips in the filmholder and use spray (non-permanent 3M) to glue the film inside? Does it affect the film? How do you store loaded filmholders if you want to keep the film flat inside and don't use glue? Is this a problem or should'nt I be worried?
-- joep jacobs (firstname.lastname@example.org), November 03, 2001
Are you using some massive film size? or just 4x5 8x10. If you're a 11x14 guy, disregard my answer. If you're smaller, that film is pretty thick -- and spraymount seems to me would attract more dust than improve picture quality, not to mention how you'd get it of the back and soak out the anti-halation coating??? I've never had problem with flatnes, but I'm not as picky as most. On the other hand, I've had some problem with dust (not that much) and with residual anti- halation and both of thoes kill a picture more than a wee bit out of focus here or there. Dean
-- Dean Lastoria (email@example.com), November 03, 2001.
Most people don't do this, so unless you are having a particular sharpness problem or you need to keep the film positioned very precisely for multiple exposures where you would be removing the holder and adjusting the camera between shots, I wouldn't worry about it.
-- David Goldfarb (firstname.lastname@example.org), November 03, 2001.
Joep: Are you having an actual sharpness problem which is not due to a lens problem, tripod shake, ground glass positioning, etc.? In other words, have you narrowed it down to film not being flat in the filmholder? There are threads on this site which split hairs to the nth degree, it doesn't mean you will have the problem. It doesn't mean that the problem really exists. It can be like browsing through a medical dictionary and getting worried about all the things that can go wrong.
-- Kevin Crisp (KRCrisp@aol.com), November 03, 2001.
Just to put some of these worries in perspective. I took a picture using 8x10 lith film. The film was slightly oversize and bowed out in the holder, but I was just shooting some tests to figure out a developer problem. I was using an old Gundlach rapid rectigraphic - its not even an anastigmatic lens. The resultant pictures when contact printed were still (my subjective opinion, mind you) sharp, whatever the hell that means. Lith film is VERY sharp film and 8x10 is forgiving of a lot of sins, so I'm not for one minute trying to say film flatness is not an issue - it is. Could the picture have been even sharper than I got? Of course! If the film had lain flat, the picture would have been sharper. The point I'm trying to make is that sharpness is a cumulative issue.
Some of these issues need to be tackled in some order of priority. Spread functions are cumulative functions. That is, sharpness is a function of an entire system and worrying about film flatness is pointless if other elements of the system have slop in them. I would argue that your lenses need to be extremely sharp and contrasty (we're talking modern, multicoated designs used fairly open in the magnification range they were designed for). Your tripod needs to be steady as a mountain. You need to expose and develop with precision. Don't stop down to where diffraction is the ceiling. Etc etc etc.
As indicated in answers above, I would start with assessing whether you have a sharpness problem to begin with (that actually affects your images). Then tackle sources of sharpness degradation in the order which will give you the biggest bang for the buck. I would look at technique, tripod, ground glass position, lenses, developer and so on and probably in that order. Although that is based on my subjective experience. If you are absolutely convinced that film flatness is the problem, sure go ahead and experiment with the glue - I'm guessing a prewash might help remove it but you'll have to experiment. Or spend the big bucks for a vacuum holder (are these even available or do they have to be designed?)
Lastly, IMHO, you do need to make a call on where you want to expend your energies. I've concluded that for the kinds of pictures I want to make (contact prints from 8x10 negs), as long as it looks sharp to the eye and folks are able to tell what the heck the darn thing is, other things about the picture matter more to ME. The search for better sharpness is an endless quest with diminshing returns. How important those incremental gains in sharpness are, only you can decide. For the kind of work I do, landscapes with old lenses typically stopped down to about f/22 or even further, I've concluded that I'm better off concentrating on making pictures and working on things like technique and seeing. Could my pictures be sharper? Of course! Would it matter? I doubt it - my pictures are likely to fail on other counts first. YMMV, FWIW etc etc etc.
Good luck, DJ.
-- N Dhananjay (email@example.com), November 03, 2001.
Thank you all for the quick respons. I would like to add some thoughts. I don't have a sharpnessproblem ( I think, hope...). It's just that I 'ran in to' the products of Sinar and Schneider. They are both producing special filmholders to keep film perfect flat (http://www.schneideroptics.com/large/hiend/hiend.htm) (http://www.sinarbron.com/filmholders.htm). The Sinarbrochure on this filmback shows also some 'nasty' examples (for what it's worth). Still, they are talking 4x5". So the problem must be huge 11x14" and bigger! I like to explore 'the chain' of sharpness and was wondering if somebody had some experience/thoughts/advice. Maybe I am getting to theoretical and maybe it is impossible to see the difference (due to stopping down, contacting negatives ets.) or maybe the 'problem' is getting less important 11x14" and bigger?
-- joep jacobs (firstname.lastname@example.org), November 03, 2001.
I work 8x10, 7x17, and 12x20 and the only film flatness problem I encounter is occassional movement or "popping" of the film during long exposures. Usually in very humid conditions. Otherwise, film flatness just isn't a worry even with these giant sizes.---C
-- Carl Weese (email@example.com), November 04, 2001.
Joep, you must have found that High End url in an old thread. It does still take one to appropriate pages on Schneider's site, but, if you didn't already know the address you wouldn't find it from the home page. Even using Schneider's own search function doesn't turn up any matches.
A likely reason for this is that Schneider has discontinued its Hi End system. Carl's experience is apparently typical, for Schnieder told me they hardly sold any, thus the decision to end production. They claimed (earlier this year) to still have stock on hand, so, if you want one, get it while you can.
-- Sal Santamaura (firstname.lastname@example.org), November 04, 2001.
It is possible for all manufacturers/marketers of photo kit to talk up a storm about things they can get you to part with more cash for.
A couple of years back Cervin Robinson tested all manner of 4x5 holders in a test for the previous incarnation of Photo Techniques ... the Sinar precision film holder did not come near meeting claimed expectations. Suspected cause? The film is held only at the edges against a full size pressure plate and the pressure exerted causes the centre of the film to bow. With a sheet loaded a pencil point can be gently pushed against the centre of the sheet and an indentation occurrs back as far as the pressure plate.
-- Walter Glover (email@example.com), November 04, 2001.
To add to my post above: Sinar also provide the option of 5x7 & 8x10 film holders with Post-It note adhesive to prevent film pop, curl, etc. A friend has some but still uses them in partnership with regular holders and has no preferences one way or the other.
Curiously, Sinar saw no need to supply 4x5 adhesive holders. Is it because they didn't feel it was necessary with the smaller format or was it so they didn't have a product competing with the more expensive precision holder? Who can tell?
-- Walter Glover (firstname.lastname@example.org), November 04, 2001.
Like DJ says: Under normal situations, it's the least of your worries. Consider, though, film sitting out overnight and cold going into a camera hot from the morning sun. Moisture condenses on the film and makes it "pop".
I've been able to simulate this with 8x10 and caused film to pop enough to really cause focus problems.
It's an easy fix, though. You simply put a small piece of double stick tape in the center of the holder- about 1/8" square. And a put a mark on the slide directly above the tape. So, if you are in one of these situations, you just push gently on the mark before inserting the holder. Store the film face to face to avoid residual adhesive from pulling off emulsion.....It works.
-- Bruce Wehman (email@example.com), November 05, 2001.
I never had problems with negs up to 8x10 but recently on 11x14 I got bubbles (an inch in diameter) of unsharpness obviously due to non flatness of the film in the cassette.This unsharpness is only visible on huge enlargements 6x7 feet ,but this is what I sell,so I have to resort to 3M glue.Blast
-- massimo vitali (firstname.lastname@example.org), March 13, 2002.