Todd Frederick , Sep 13, 2002; 08:06 p.m.
With regard to the question asked below concerning film flatness in
cameras where the film bends back on itself around inserts (Mamiya,
Hasselblad, etc) I ran a field test. I had a roll of film in my
Mamiya 645e for at least two weeks, on exposure #1. If the film
buckled, it would appear on frame #2. I ran the roll on many objects
around the house and yard. The photo above is frame #2, full frame,
and, if the buckling occured in the image area itself it would appear
as a fuzzy band unfocused across the image horizontally. The aperture
was f/5.6. Both frame one and frame two are identical showing no
evidence of an out of focus band. I can only assume that, with the
Mamiya insert, the bend occurs between frames. Looking at the insert
construction, that seems to be the case. When I processed the film,
I felt the film for evidence of uneveness, and, yes, there was a
definite bump across the film where it bent back on itself...it felt
like a small "speed bump" in a road. However, based on the images I
produced, some taken in quick succession, and some waiting 30 minutes
or more, all images are sharp with no evidence of an out of focus
band. I feel much more confident using this camera now, after
running this simple test, and I am not concerned with out of focus
areas on my images due to film bending. However, I do think it is
wise to load the film just before using the camera, and not to leave
the film in the camera for extended periods of time, just to be on
the safe side.
Jay . , Sep 13, 2002; 08:40 p.m.
>>With regard to the question asked below concerning film flatness in cameras where the film bends back on itself around inserts (Mamiya, Hasselblad, etc)<<
Todd, I have no film flatness problem with my Hasselblad backs (3 A12's with "12" in the release button, the generation just before the current ones with darkslide holders)even if I leave film in them for a month (which rarely happens but it has happened). I can't speak for the inserts in the Mamiya 645E but there might be something more than just smoke and mirrors to the fact that a Hasselblad film back alone costs more than the entire 645E kit with insert, lens and winder.
Charles Barcellona , Sep 13, 2002; 09:09 p.m.
There is an article on the Zeiss website about film flatness in rollfilm cameras. Its informative, but... it seems that the "problem", can only be seen on film in the most critical shots, ie test targets.
Todd Frederick , Sep 13, 2002; 09:42 p.m.
Jay and Charles,
I did not have film flatness problems with either Hasselblad or Mamiya inserts over years of use. The only problem I had with Hasselblad backs was light leaking in the baffles, which should be serviced and replaced every two years or so, under heavy pro use. I **never** had any problems with Mamiya film inserts. I think they are very well designed, and the film bend is at the space between frames. Mamiya 645 camera systems and inserts have been around since the mid 1970s, and the inserts have remained unchanged and are used in most Mamiya 645 system today. I am convinced, by my field experience over 30 years, that these two systems (Hasselblad...very expensive; and Mamiya...very economical) are designed to avoid this problem.
I read the Zeiss article, and I seriously think it makes this to be much more of a problem than actually exists, based on my personal field experience. "Bench Testing" is quite different from field photography. I've enlarged 645 negs to 30x40+ with no problem and will be using my new lightweight AE 645e tomorrow with similar images in mind. I'm not concerned, but am pleased that I ran one more test on this today.
My advice...go out and take photos. Not to worry!
Mountains from molehills, IMO.
Charles Barcellona , Sep 14, 2002; 04:06 a.m.
I agree Todd - I've never seen the problem. BTW, the same "problem" exists in 35mm films.
Olivier Truan , Sep 14, 2002; 09:24 a.m.
Todd Frederick , Sep 14, 2002; 09:47 a.m.
Oliver,
When I try to access you test, it says "URL Not Found." I'll try again later.
Olivier Truan , Sep 14, 2002; 10:00 a.m.
Sorry, my mistake, it was not selected for public view. Now it should work!
Sal Santamaura , Sep 14, 2002; 10:36 a.m.
In my response to Todd's first thread, I said:
"Actual photographic implications, if any, depend on your specific working conditions, and should be determined by individual test."
It's heartening to see that this time several people have taken that advice rather than dismissing the problem as fantasy/conspiracy. By the way, test targets aren't the only flat subjects out there. Anyone photographing planar objects at large apertures with a reverse curl back will suffer the same problems that Olivier's results revealed. Also note that, contrary to intuition, poor focus caused by this deficiency will become more severe with shorter focal length lenses.
Todd Frederick , Sep 14, 2002; 11:19 a.m.
Oliver...Try as I may, I still can not access your URL site for the test you ran.
Also, my point was not that there is no back curl (or whatever you want to call it) but it seems to fall on the space between frames with my Mamiya 120 inserts. Has anyone tried measuring that? I might try later today...it's not possible to measure while in the camera since the insert must be in the camera to turn, but I might try rolling it by hand outside the camera and measuring and marking each frame on the paper to see where the space between frames falls on the insert...I'm guessing it will be the point where is bends.
I have examined the roll I took again and again with a strong lupe, and nowhere are there any bands of unsharpness across any image frame, even the one that was bent for three weeks.
I'm going out now to use the camera for some portraits at the beach.
