Vivitar Series One 90-180/4.5 K-mount lens

I received my new Pentax K10D today. The main reason I got it is because I
have some excellent manual focus lenses that I wanted to use on it. One of
those is a Vivitar Series One 90-180/4.5 K-mount lens--an extraordinary
lens. Unfortunately, there is a metal collar that partially surrounds the
rear element that prevents the lens from mounting on the camera. The other
K-mount lenses I have mount without difficulty. Has anyone had any
experience with this problem. If I could get the collar off the lens and
could grind it down, I believe the lens would fit but I am not sure how to
do this (it would be too risky to try to do this with collar mounted because
it is so close to the rear element. Any help would be appreciated. Thanks

 

Before doing radical surgery that would minimally damage the resale
value and worse, damage the lens, ask yourself what is the main use of
this lens? It's a flat field variable focal length macro lens. Do you
use this lens at infinite focus a lot? I've found that it is prone to
flare (Olympus OM mount) and don't use it a lot as a short telephoto.
I use it for macro work. I'd put a short extension tube on it and see
if it works for your needs. That would eliminate the ability for
infinity focus though.

I did have to do minor surgery on my lens, one of the mounting screws is
positioned in a way that can damage an OM4 mount reset button, so I
filled in that one point with epoxy. But that's about as far as I would
go for "surgery" on this lens.

One thing about the lens, it does give the biceps a workout!

JD

 

Thank you, thank you. Your solution was so elegantly simple that I am
kicking myself for not thinking of it. My main if not sole use of the lens
is for macro work so the loss of the ability to focus to infinity is a small
price to pay. I have a set of extension tubes and your suggestion worked
like a charm even with the shortest tube

David Goldstein

 

Glad it works for you. I forgot to mention that whenever you put an
extension on a zoom, you lose the constant focus capability. But that
just makes this Vivitar like a Vivitar 28-90 - a varifocal lens. Now go
shoot some bugs.

JD

 

go ahead shave it down

I also own the 90-180 Macro zoom. You just have to take off the 4 little screws in the SIDE of the mount. That will allow you to take the baffle off. Grind to your hearts content and re-install (if you haven't lost any of the teeny tiny screws.)
Very painless and AFAIK would increase value to all Pentax users....