I finally got around to trying something with this lens modification
(defeating the auto diaphragm mechanism on old style 42mm screw mount
lenses). I tried it out on a Kaligar Auto 2.8/135 42mm screw mount.
(I wonder if anybody knows anything about this lens. My research
didn't turn it up and talked about Kaligar/Kalimar as MF cameras and
lenses with an odd 44mm screwmount. This lens fits a K-M42 adaptor
just fine, however.)
I removed the rear plate of the lens through which the stop down rod
protrudes. This consisted of unscrewing three screws and lifting the
plate out. The exposed mechanism didn't offer any simple way of being
disarmed so I ended up filling the hole the rod goes through with
beeswax, softened in my hand. I then stuck the rod back in the hole,
just far enough to hold it in place while replacing the plate.
This seems to be working fine. I didn't measure the thickness of the
back plate, but it's around .25 in at the spot where the rod goes
through, so there's a fairly sizeable plug of wax holding it in.
Melting paraffin into the hole, with the plate removed, might be a
slightly better solution. I'll keep an eye on the plug. A worst case
failure would seem to be a small lump of beeswax in the mirror box,
if it didn't remain stuck to the end of the rod.
Thanks to everybody for their advice and I'll let the list know how it goes!
I haven't taken many pictures with it yet, but at f2.8 it's a nice bright lens!
At 8:57 PM -0400 5/14/05, P. J. Alling wrote:
You don't want to do something that if it fails will damage you camera.
Alan P. Hayes wrote:
Without doing it I can only use the lens wide open, because the new
cameras have no way of actuating the stop down rod at the time of
exposure. If the rod is pushed in permanently then the aperture
ring actually stops the lens down. That way I can use it at all the
f stops, metering at taking aperture on Manual mode (on the istD).
I probably could use it in Av mode too...hmm...
I'm thinking of trying to push it in and then sticking some wax in
the hole. If it holds it ought to be reversible.
At 4:47 PM -0500 5/14/05, George Sinos wrote:
I'm just curious, Alan. Why do you want to do that?
GS
On 5/14/05, Alan P. Hayes <[EMAIL PROTECTED]> wrote:
>
I've got a couple of SM lenses with the little push rod arrangement
for stopping the lens down. Is there a simple solution to keeping it
pushed in when using the lens with a screw to K mount adapter?
--
--
A man's only as old as the woman he feels.
--Groucho Marx
--
Alan P. Hayes
Meaning and Form: Writing, Editing and Document Design
Pittsfield, Massachusetts
Photographs at
http://www.ahayesphoto.com/americandead/index.htm
