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For my 1Ds II, I get the following measurement:
EOS flange to metal top (in front of focus screen): 6.8mm
EOS flange to mirror front (when mirror is up): 7.3mm
So if I reduce the rear edge of the M42-M39 adapter slightly to stay clear of the metal top, I can place the rear element closer to its original FD distance. Currently the rear element protrudes about 1.2mm out of the M42 adapter, making its position about 6.86mm deep from the EOS flange (to get original FD configuration it should be 7.4mm). With the rear element and the 2nd element separation just right I did manage to get infinity in focus.
My setup procedure:
First with the M42 adapter mounted on my 1Ds II, I screwed in the M42-M39 adapter (with rear element glued) until it hit something hard (it hit the metal top not the mirror, because the camera could just fire off without error). Then I backed off very slightly. The angular position of the M39 adapter was marked and fixed temporarily with tape.
Next I use a 3M scotch tape stick on the front of rear element. With the main 85mm lens laying head-down, I put the M42 adapter on the rear of the lens. and turned the focus ring towards infinity util the 2nd element hit the rear element and pushed the M42 adapter upwards. Then I reversed the focus ring until the M42 adapter stayed flush with the FD mount ring. And I backed off slightly more. After this I set the focus limiter of the focus ring to this new position.
Then I fixed the M42 adapter to the lens and mounted the lens to the camera and test the infinity focusing. After a couple of times of testing and trimming the M39 adapter I managed to get infinity. But unfortunately since I only tape the rear element and not the 2nd element, with all this head to head collision (and sometimes I turned the M42 adapter when it was topping the 2nd element) I caused a slightly smearing of the coating on the elements . But this is a small price to pay for getting infinity.
Edited on Oct 15, 2009 at 07:50 PM · View previous versions