Posted by Les on April 27, 2001 at 15:11:20:
In Reply to: Re: Checking of Focal Plane shutter is accurate? posted by Pete Gregar on April 27, 2001 at 13:18:06:
Calumet sell a "digital shutter tester" for aroun $80. Before you buy that. I'd set up a couple of tests. My favorite is to find a south facing wall It's best find something uniform-without windows--all brick or all siding.
Bring you 35mm along and load it with the same film as the other camera.
Shoot equivelent exposures 1/60 @f8, 1/125@f5.6,etc, whatever
the meter reads. Shoot as many as the lens will allow (on a sunny
day you won't be able to shoot wide open)
now repeat the same equivelent exposures with the other camera.
Really old graphics used odd shutter speeds like 1/270. I'd
generalize those to the nearsest normal shutter speed, like 1/250.
Make notes, place id cards in the shot so you know which shot was
taken at which exposure
Process all the film the same way. Then look at them on a light table or window. The 35mm film is our standard. All of the frames should have the same even tone to them, and may look a bit under exposed. Now compare the density of the focal plane camera with the density of the 35mm.
If all the LF film is uniform then the camera is within tolerances and you should go out a buy a lottery ticket asap. The negs that are denser are the speeds that are slowing down. If the film is all over the place, then its time for repair or the shutter tester to find out what each speed really is and more importantly, if it's consistant. If the target is nice and smooth and you've set the camera up square to the target you may be able to see any major variation from top to bottom.
The trick with this is to pick a day that has consistant light over about a 1hr period