OK- so the world is not flat and you think your film is…NO. Film flatness has always been a concern of LF photographers but something most roll film users never give a second thought…time to wake up. Think about it…if you are shooting 120mm film which is wrapped around a spindle then it is fed through a system of rollers in your camera thats bending and flexing it, this is a serious problem…especially if you leave a roll in the camera for a while…a half “s” cuve will form and as a result that neg will most likely not be as sharp as the next (this varies from film to film based on the type of base material used, backing, ect…). If you are shooting at say f8+ for most of your works then this is much of an issue but a 2.8 or 4 it is huge. Humidity and temp also effect this…a lot! So where does this leave us….
My technique is this…load the film just before shooting and shoot the whole role, especially if it is going to be wide open at 2.8. Don’t leave half exposed roll in your camera…and Don’t expect the first or last frame to be as sharp as the middle frames…not going to happen.
Do this test…put your camera on a tripod and focus at an object say 10 feet away…then shoot 2 frames focusing at the same point at say f2.8….then do this at the same point at f8….then let the film sit in the camera for a few hours or overnight and do it again at f2.8 and f8, now process your film. What you will see is that some negs are sharper than others even tho the point of critical focus has not changed.
This is just food for thought for those of you who like myself like to shoot film wide open and sometimes get frustrated with a focus shift due to film flatness or lack there of…it is not your fault but it is a another level of variability you now need to take into consideration. By the way…one of the worst camera’s for this issue is a (drum roll please)….Hasselblad…no kidding. Look at how the film is loaded into the holder…very scary indeed!
Additionaly, don’t think this is limited to film…ever consider just how accurate your alignment is with your digital system…not as good as it could be!
I’d like to thank Bill Maxwell for of Maxwell Precision Optics for his insight into this area and for pushing me now one step closer to the edge…