Fixing an adaptall to M42 adapter

Jesito · Expire: 2015-01-07

Hi colleagues,
Before attempting to modify the CZJ Planar, I've been doing some exercises to get more and more confidence with the lens handling.

A couple of days ago I received the Tamron 135 2.5, that was fitted with an Adaptall to M42 adapter.
The problem with this adapter is that the aperture remains always wide open if no one pushes a pin in the base of the adapter. This is for "automatic" M42 bodies that allow measuring wide open and closing the diaphragm before firing the shutter. But not useful for the Pentax or the Canon, that don't have that mechanism.

So I thought in forcing the pin down to allow using the aperture ring. The mod has to be reversable, I don't want (if possible) to do any physical change (damage?) to the lens. One never knows which camera body will have tomorrow... Wink

I tried several tricks, but no one was too stable to keep using it. After much thinking, I found the solution: a piece of ballpen ink tube:

Getting to this was not difficult, just to unscrew the three screws on the base of tha adapter, the same way backwards to mount it:

And now everything works as expected, without the need of pushing the pin:

and a couple of samples, closed and wide open:

BTW, nice bokeh. Attila, you were right, it's a nice lens!.

Jes.

Jieffe · Joined: 04 Nov 2007 Posts: 754 Location: Belgium

I did the same trick but watch out for the height of the ball pen tube. If too long, the adaptall could be stuck on the lens and it will be very difficult to remove it ...

Believe me, I know what I'm talking about Wink

Jesito · Expire: 2015-01-07