Quote Originally Posted by Jim Jones
Both C and D mounts have 32 TPI. The D mount is 5/8 inch. I use the old series adaptor rings to reverse mount movie and enlarging lenses on 35mm and LF cameras. A series 6 or 7 retainer ring epoxied, thread outward, on a lens board or body cap, can be used with step-up rings for about any size lens. Some old camera stores have boxes of adaptor rings hidden away somewhere to mount the lens on the retainer ring. The effective f/number is quite high with movie lenses reverse mounted for micro work. Thus, diffraction limits resolution, even when wide open.
Ok. Now that I've read up a little bit more on C mounts and different mounting threads especially at this web page, I have a few more questions about mounting a C mount lens reversed.

I found that the C mount has a 1" diameter with 32TPI threads but reverse mounted, this mount is irrelevant to me as it's going to be outside, right? I couldn't find any information about the filter threads the lenses have which is what I need to reverse mount them with some sort of step down ring. I assume that just like SLR lenses C mount lenses come in a variety of filter diameters but what is the thread pitch for filters? Is it the same as for 35mm SLR filters? That would make life a lot simpler? (I couldn't find the specs for filter thread pitches for any camera)

Secondly, if I use a BR-2 ring to get from the F mount of my extension ring (maybe a bellows, but I am coming to that later) to a 52mm male filter thread, then is it just a matter of finding the appropriate step down rings to get to the filter size if the 25/1.9 Ektar, for example. If the filter pitch sizes are the same, I could just screw it on, right?

Finally, I can see that a bellows is not far away in my future . Unfortunatley, I've never handled one of these and all my knowledge is from internet forums and books. I know the Nikon Bellows system comes with male and female F-mounts on each end but are there generic bellows that I could get cheaper with maybe just screw mounts on them that I could just adapt with step down rings or the BR-2.

How usable are the C mount lenses with extension rings for macro - or is bellows a must? I just spent a bunch on a tripod and would like to defer the bellows for some time or keep its cost to a minimum.

I know I am asking a lot of naive questions, but I really appreciate any help in this area.