http://ratx.narod.ru/tests/mir47k/ # this is the page that persuaded me to buy it. (No knowledge of Russian required...)
WRT your question about the rear filter forming part of the optical system, glass has a greater "optical depth" than air, so removing the filter effectively shifts the whole lens slightly towards the film, altering the focus.
S
PS Made by the VOMZ tank-periscope factory - how cool is that? ;-)
Ian bromehead wrote:
Fellow pentaxphiles
There seems to be a growing number of russian lenses arriving on the scenes,
and some notable specialists such as Herbert Keppler, seem to suggest they
can be great value. I'm taking my time searching for reasonably priced wide angle/fisheye,
clearly this type of glass means lots of pennies in most cases.
I came across a russian MIR-47K 20mm f2.8 Pentax K mount, but there's
precious little information from users' experiences or tests.
I did find a few threads concerning mirrors in some bodies hitting the rear
filter mounts, seems from those threads that my pZ-1p wouldn't be affected
!!
Anyone confirm, I don't dare think of the risks Seems also that 1 of the supplied rear filters HAVE to be used all the time,
since they're part of the optical system. How come ?
Anyone have any actual usage experiences with this glass ?
Thanks
Ian
