Using Pentax Super Takumar M42 mount 50mm/1.4 on a Canon 3..

Archived from groups: rec.photo.digital (More info?)

Hey,

I just bought a used Pentax Super Takumar 50mm/1.4 lens. The lens has a
Manual/Auto switch for aperture control. When I switch to Auto and
rotate the aperture ring I can see the aperture blades moving to set
the aperture. In manual mode nothing happens when I rotate the aperture
ring.

So how exactly do I use the lens? Ofcourse, I will experiment and learn
but thats after I receive the M42-to-EOS adapter that I've ordered.

Btw, the focus ring is damn smooth and the lens looks awesome
Thanks,

Siddhartha

Archived from groups: rec.photo.digital (More info?)

"Siddhartha Jain" <losttoy2000@yahoo.co.uk> wrote:
>
> >I just bought a used Pentax Super Takumar 50mm/1.4 lens. The lens has a
> >Manual/Auto switch for aperture control. When I switch to Auto and
> >rotate the aperture ring I can see the aperture blades moving to set
> >the aperture. In manual mode nothing happens when I rotate the aperture
> >ring.
> >
> >So how exactly do I use the lens?

Asahi Optical included that switch when they introduced the Super Takumar
lens lineup, to maintain backward compatibility with their older models of
SLR. The Super-Takumars had an automatic diaphragm, and it required a
coupling inside the camera body that pushed on a pin, stopping down the lens
at the moment of exposure.

The coupling mechanism was not present in older models of Pentax bodies,
which used preset lenses. By including the auto-manual switch, it enabled
the lens to be used on those older model bodies.

The Spotmatic and ES models all supported automatic diaphragm lenses, and
there was no need to use the auto-manual switch when the lenses were mounted
on those newer bodies. In fact, the switch was designed so that it could
not inadvertently be nudged from the auto to the manual position if the lens
was mounted on a Spotmatic or ES body. Do not try to force that switch.

You can use these lenses in stopdown mode even on cameras that do not have a
preview switch, by first mounting them on the camera and then moving the
switch to the manual position. Do not try to put the lens into manual mode
unless it is first mounted on a camera--there is a very tiny pin on the lens
mount that must be pushed in or you will break the switch.

Asahi could not have foretold it at the time, but the auto manual switch
enabled these lenses to not only maintain backward compatibility, but also
to remain forward compatible with digital bodies.