 M Rayburn |
Flash sync problem
I recently started getting a dark area on one side of the frame, not quite a black band and usually at the top of the frame. Shutter is at 1/125 which is the rated flash sync with this camera, motor drive also on. I'm using studio strobes, Excalibur 6400's. I'm thinking just go to 1/60 second on the shutter and this may clear Any ideas or comments.
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Jon Close |
The two samples look like a shutter problem to me (2nd curtain sticking or closing too soon).
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BetterPhoto Member |
I would certainly have the camera looked at, but it has been my experience the the focal plane shutters travel along the long axis and would leave one of the short sides underexposed. But definitely have it checked out and talk to your clerk about the problem you're having. They just might think of something and save you the unecessary repair bill if they're good.
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Jon Close |
"... it has been my experience the the focal plane shutters travel along the long axis ..." That was the case with older/simpler SLRs, especially those with cloth shutters. The FM, and most modern SLRs, have vertical travel shutters.
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M Rayburn |
Thank you for your replies. I think I've found the solution in an e-mail I received: Studio flash, especially with The accepted rule of thumb is 1/4-1/2 of your camera's fastest X-sync Even with brand-spanking-new ultra-modern equipment, in studios I You think that sync is sync, but speed lights are much smaller flashtubes with drastically shorter discharge pulses. An on-camera flash may dump in 1/3000 sec at full power. A studio flash at full has much more energy to dump and does it over a longer period of time for greater light output - some units have flash durations as long as 1/200 sec. Add in a delay for the wireless trigger (even a 5 millisecond delay is 1/200 sec) and that plus your discharge then comes to a full 1/100 second, longer than a 1/125 sec sync.
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BetterPhoto Member |
The reason for the slower shutter speeds is that your focal plane shutter is made up from two curtains on a tension spring system. When the shutter is released, the first curtain moves across the film surface, opening the shutter and the second follows a predetermined amount of time after the first one has begun moving. So there is open space across the negative up to 1/60 of a second exposure. 1/125th on up is really neat. 1/60th is about the fastest that the shutters can move, so at 1/125th the second shutter starts when the first is only about half way across the film negative so that the film gets equal exposure for half the time of 1/60. At 1/250th, the second shutter follows the first when it is 1/4 of the way across. At 1/500, one eighth across. 1/1000, only one sixteenth across, which in 35mm is equivalent to about 2 millimeters of the film exposed at a time, but giving equal exposure to the entire negative. Now, with flash photography, above 1/60 shutter speed, not all of the film is exposed at the same time, only one half of its surface or less, hence the lack of lit exposure by the flash. The flash went off when only of the portion of the film could record it.
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