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Forum: Troubleshooting and Beginner Help
07-23-2013, 02:22 PM
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The old Asahi documentation on Takumar lenses notes that there should NOT be any oil or grease used on the diaphragm or linkage. They originally coated some parts with dry-lube film, and they say NOT to wash the parts with solvent (which would promote corrosion, etc), but to carefully disassemble and wipe each part carefully to remove any oil. Diaphragm blades often had a black-oxide coating that is not rust-proof, and so they said not to touch them with your fingers, but to use tweezers or wear gloves to assemble.
I've followed similar steps to cure sluggish diaphragms, but usually "burnish" sliding parts with moly-disulfide powder, wiping off well until nothing visible wipe off.
Pentax lenses have far fewer problems with such issues than some other makes of the same time period. I've seldom found a Canon FL lens that doesn't need to be serviced! It's common on old Canon FT cameras to find uneven exposures in bright light because the diaphragms are slow to close to small apertures. On film cameras you can open the back and look through the shutter curtains as you fire with high shutter speed and f16 settings, and see if the lens opening is the same on the left and right sides.
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