I recently purchased a Computar 25mm f1.4 and a RJ c-mount adapter, but I can not hit focus. It appears the large metal back does not allow the lens to fully thread into the adapter. I am only able to rotate the adapter one half a revolution before the lens stops it. Any advice?

Just purchased the same lens hoping it would be a good match for my computar 25mm F1.3, which has become a favorite in our new photography business. The F1.4 lens has 6 blades versus the F1.3's 3 blades, so on paper it appears to be superior, but of course there is no way to know since I am running into the same issue you are.

I'm using an older hawk c-mount adapter on my GH1, and the lens has extremely close but unusable focus. On the adapter at infinity focus, I can focus on an object at a little less than a foot away. Removing the adapter and putting the lens as close to the sensor as possible, I can then focus on an object about two feet away. The lens rests against the outside of the camera, and it doesn't seem that the rear glass is too close to the sensor, but I do not want to take a chance hurting the mechanical shutter so I have not taken any pictures with this setup.

It seems the solution is to modify the lens so that the bottom glass is closer to the image sensor, but again I am worried about hurting the mechanical shutter. Not quite sure the best way to go about this. It was a cheap lens, so it is ripe for amateur modification. Any advice?