[netrex]

I bought the Vivitar 200mm 1:3.5 Screwmount. I thought it was M42, but it wasn't.

As you can see here on these photographs, the mount on the part that's screwed on at the end is slightly bigger than an M42 mount. The Vivitar is on the left and the one on the right is the Petri 135mm 1:2.8 M42 lens.

On the second image I've screwed off the part at the end of the Vivitar. The screwmount that is there is the same diameter as M42, but the threads are not the same, so, as you can see on the last image, my original Pentax M42 to K-mount adapter can only be screwed on at the edge, not completely.

Does anyone know which adapter I need to make this lens fit on my K10D? This Vivitar lens has 18 aperture blades, so I really want to use it.

[Asahiflex]

I'm 100% sure you'd need a T-mount adapter. See here: T-mount - Wikipedia, the free encyclopedia

[netrex]

Thank you for your reply Asahiflex! I really appreciate it I'll see if I can get my hands on the right adapter so I can use this lens.

Thanks again, greatly appreciated