I have an Elmar 135 f4 (M). Can I unscrew the head?
Yes!
>>I can only unscrew a little aluminum ring under the aperture ring. It uncovers some screws. Should I go on?<<
Yes, I think so.
>>If it unscrews, I could maybe adapt the head to a Pentax zoom tube.<<
The part that gets unscrewed is the lens itself. The bigger part left behind is called the focusing mount. Unfortunately the 135 cannot be attached to a Pentax zoom tube. My technician used the Pentax zoom tube because it happened to fit the 90 lens, that's all. He made another tube for my 135 lens, which can only be used for the 135 lens.
Best regards
Sung Nee
