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Flange focal distance and lens-film parallelism

10 points · submitted Jul 2026 by u/savyexe

I have this Yashicaflex (new) model A from 1958. It's in amazing condition, lens is crystal clear, shutter fires accurately, even the self timer works; but after running a roll through it some pictures came out like this, with the left side of the image in focus and the right not in focus (also not in focus at infinity). My guess is that the camera was dropped at some point. I know the lens assembly is mounted to the body using washers, and that adding or removing them would fix the problem. My question is if there's any method to know how many to add/remove on which corner (and the thickness). I also have a Nikon FM2 with the same problem. Any advice would be HIGHLY appreciated...

7 comments · 100% upvoted · source · other discussions

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jagoedho 3 points · Jul 2026 · Commercial Repair Person

If it has impact damage, shimming isn't going to help. TLRs are very sensitive to fall damage. Parts replacement is the only proper way to go. Fall damage TLRs should be avoided. The metal focusing parts on Yashicas are extremely soft.

savyexe [OP] 1 points · Jul 2026 · Tinkerer

I took the camera apart when it came from japan (because it was super dirty) so i've seen the mounts. If they're soft they'd be susceptible to be bent back onto shape no? About the calibration i've seen people use a digital camera, lens to lens, glass plate on the film plane, and focus both cameras to infinity, but i'm not sure how that would work. (Also from and old camera repair manual i saw i'm wondering how hard building a collimator)

jagoedho 1 points · Jul 2026 · Commercial Repair Person

If you can get them within 0,02mm after reshaping you might shim it out

gotDeus 2 points · Jul 2026

For your nikon, you use shims on the bayonet mount. You’ll need to use a calibrated micro depth gauge and measure each corner. I’d Measure the mounting plate flatness or for warping, or the plate that its mounted on to the body. For the yashica, i’m guessing the lens mount is warped. I’m not sure if that is done with shims though.

savyexe [OP] 1 points · Jul 2026 · Tinkerer

Any recommendations on a good micro depth gauge that won't cost me an arm and a leg? The Nikon i took apart completely to fit a new shutter so i've seen the shims, my guess is that the new shutter somehow changed the spacing (?). And about the yashica, the lens is mounted into a flat metal plate and that plate is mounted into the focusing arms with shims, so i could technically add or remove shims to make the whole lens more parallel. The problem is i don't know how to check calibration, i've seen people use a digital camera, lens to lens, both cameras set to infinity, and a glass plate on the film plane, but i'm not sure how know if i have to add or remove shims from that. From an old camera repair manual i saw instructions on how to build a collimator, but it's not completely clear and also doesn't say anything on how to use the damn thing

gotDeus 1 points · Jul 2026

Its possible, even if you did not move the spacers around there could be something that moved. The depth gauge i cannot recommend cheap ones for sure. There’s tolerances here measured at .01 mm or less.

for the tlr i guess you can play with the shims, as for measuring distance the digital route probably wont work. i’d go the ground glass route with a strong loupe to check the corners, i’d imagine this to be twice the work cause you’d need to do both the taking lens and the viewing lens to ensure flatness and calibration on both.

savyexe [OP] 1 points · Jul 2026 · Tinkerer

Oh boy this is gonna be a huge pain in the rear but i guess i don't really have a choice, 120 is not cheap and i can't go around shooting out of focus shots :/

As fot the Nikon guess i'll just look into getting a decent depth gauge that can measure down to .01mm