an old engineer friend of mine once said "if it jams force it, and it breaks it needed replacement anyway" (thanks Paul).
With this philosophy clearly in mind I had a go at fitting my lens onto a new adaptor I bought on eBay in an attempt to mount a Computar 12.5mm f1.3 TV lens onto my G1.
I've previously bought an Elgeet lens and RJ Cameras adaptor which worked fine, and looked like this.
But the Computar wouldn't fit in the recess (by a long shot) and RJ Camera said it couldn't be done. So I bought another adaptor from a fellow on eBay called hawkpeng2003, which I expected would be close ... what follows is my small journey to get it going...
The bottom of my lens looks like this:
and comparing it to the RJ Camera mount:
it just clealy wasn't going to fit.
Well, the diagrams from Hawkpeng2003 on his site looked promising, particularly this one:
Here is my adaptor (and the lens in the background)
The dot you see on the lower left is the alignment dot. Note also the chamfer on the contcentric inner edges of the mount. The actual dimensions of the lens matched the dimensions of the mount in the diagram above from HawkPeng2003, but it did not take into account the square edges on the lens, and his adaptor has chamfered edges.
All of them other edges on the lens were within the sizes he quoted except one ... the second inner edge.
So armed with my trusty Leatherman I set to work to carefully file that second inner edge back. Here's the result:
Now, prior to working I used some masking tape around the mounting thread to form a protective 'tube' which I pinched off. This was just to keep filings and finger prints off the lens.
Now as you can see the lens and the mount will go together better:
and boy, its close as you can see ... but the chamfer matches (well perhaps its got some clearance too).
but it fits and finally I can screw it down properly so that the alignment mark comes very close to perfect.
the final check is that the alignment mark on the adaptor comes quite close enough to that of the lens to give me quite good infinity focus (even with the magnifier).
Here it is on the camera
and it takes great images