I own the SMC 500 4.5 and use it on my K10D, so I checked out my lens to see
why someone would need a K adaptor for it. The site calls it f4.6, but if
you look close at the photo it says f4.5.
The part of the lens that mounts to the camera is removable by unscrewing a
collar just behind the focus meter. It looks to me like the mount piece of
the lens in question was either lost, damaged or was for a non-K camera (M42
or maybe medium format, if those options were available), and the owner of
the lens wasn't able to find a proper replacement. The original part
allowed for 52mm filters to be mounted internally, so that couldn't have
been his only reason for making the custom part. The original also allowed
for the whole lens to be turned relative to the camera (see the knob near
the back here:
http://kmp.bdimitrov.de/lenses/primes/extreme-tele/K500f4.5.html), so his
custom part is missing that feature.
I should note, that removable mount feature has almost cost me the lens a
couple times. Damn thing comes loose easily, and you'll be out shooting
when suddenly you're holding the oddly light camera with one hand and have
to scramble to catch the lens!
John
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----- Original Message -----
From: "Mark Roberts" <[EMAIL PROTECTED]>
To: "Pentax-Discuss Mail List" <pdml@pdml.net>
Sent: Friday, November 28, 2008 1:39 PM
Subject: Re: Custom Machinist doing gods work...
What am I missing here? My Pentax K500/4.5 mounts just fine on both my
K1000 film body and my K20D digital body, with no problem in focusing to
infinity. Of course, focusing is manual unless I use my F1.7x AF
Teleconverter behind the lens...
The front mount on that adapter looks very "different" and the
connection between the adapter looks odd.
I'd guess that this lens was modified for some other camera mount and,
after it changed hands a few times, someone had a custom adapter made to
make it fit a K-mount camera again.
Weird.
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