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07-22-2011, 11:30 AM   #1
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Lens compatibility help!

I have Pentax K20D.
I just ordered a Vivitar 28mm K-mount fully manual lens. It doesn't fit! It has a the correct 3 tabs but the black thing that extends into the body is larger than my other lense and makes it incompatible. I can get it into my Pentax PZ1 film body. I can't find any where that says there are some K-mounts that won't fit on DSLR bodies. Is there an adapter fix or am I screwed (no pun intended)?

07-22-2011, 11:45 AM   #2
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AFAIK a k mount is a k mount. Please post a pic of the lens showing the front inscriptions as well as the mounting.
07-22-2011, 11:53 AM   #3
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Never mind. I figured out how to remove the too-large flange. Seems to work fine without it.
07-22-2011, 01:51 PM   #4
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Some older lenses seems to have a larger flang. Mostly you can remove it, adjust it's length en mount it again.
Removing it totally could cause damage to you're lens when the lenscap fall's of while stored.

You really aren't the first to stumble on this problem

07-22-2011, 02:07 PM   #5
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This is a known problem with some Vivitar lenses. The problem seems to be that the guard that protects the aperture lever is longer than on the genuine Pentax lenses, and hits the power contacts for the SDM auto-focus motors.

Quite a few people have reported that it is easy to grind or cut the offending guard down to size, or remove it altogether.

The other major k-mount incompatibility to watch out for is the dreaded Ricoh pin. On some Ricoh automatic cameras, there was an extra pin, used only on Ricoh cameras, that can get jammed in the AF screw drive and make the lens extremely difficult to remove. Again, the Ricoh pin is relatively easy to remove and serves no purpose on a Pentax camera.

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