Needing to replace the rear lens on a TLR.

waynecrider · Oct 24, 2008

I was given a YashicaMat 124G with a bad rear lens. Luckily I have a replacement on a YashicaMat 124 camera with a bad shutter, both Yashinon lenses. By the time I buy a spanner wrench and lens sucker I'll still need to replace the seals which I have material for. The big question is whether I can run into problems with needing shimming or such for collimation? If I repair it myself I get new tools; If I send it out the camera repair will probably be the same price. What do you think.

Jeff L · Oct 24, 2008

Send it out. I say this not knowing what your repair skill level is.
If it was me- I'd send it out.
If it's just a bad shutter in the one, can you not just replace the shutter from the one with the scratched lens?
I'd be inclined to keep the complete good lens no matter what body it comes from or goes into, and change the shutter.
I have a 124G and find it very good.
Jeff

John Jarosz · Oct 24, 2008

I'm not familiar with that camera, but can you replace both cells from the unit with the bad shutter into the one you want to save? The mechanical tolerances on the physical mounting of the lens cells is probably the same.(you could probably verify this by taking some measurements with a micrometer, if there is room) On the off-chance that the cells are a matched set, replacing both cells may be a better idea.

John

John Koehrer · Oct 24, 2008

Not having one of those lying around to look at, some of the tlr's have a light shield around the rear elements & you might have to remove that also.
If not, there's no need to buy spanners. Take a pair of needlenose pliers & grind the tips to fit the spanner notches. If your thinking of swapping the entire shutter you'll need to remove the rear element anyway since the mounting flange for the shutter is under the element.

greybeard · Oct 24, 2008

The big question is whether I can run into problems with needing shimming or such for collimation?

I am under the impression that the viewing and taking lenses for TLRs have to be matched in focal length, since normal manufacturing tolerances aren't good enough to allow complete interchangeability. This is probably only important for close-up work (i.e.--portraits in dim light) once the two lenses are positioned for infinity focus. It would seem that the best bet would be to use all the glass from the body with the bad shutter, and look closely for an adjustment (probably on the viewing lens mount) where the infinity adjustment is made.

ic-racer · Oct 24, 2008

I believe it should unscrew. The shims (if any) help with flatness of field and should not affect collimation. The front and rear elements of a Rolleicord I recently acquired came off easily for cleaning.

(there was a url link here which no longer exists)

waynecrider · Oct 24, 2008

Gee what happened to this thread. I can't read the responses without scrolling off into the wild blue yonder. Is this a problem on the APUG end?

Good point John J; I may need to do that but I think I'll try just the rear element for now.

JK, it does indeed have the light shield around the lens and it can't be removed.

My skills are good and I need to pull apart a Rollei 35 to see whats up with the film wind crank so I'm going to buy the tools. Besides the new camera seems to have a nice shutter in it an not needing service.

P.S, ic-racer, can you send me a link or PDF on that diagram? It's sized like a 30x40 inch print on my 15 inch computer screen. Thanks.

ic-racer · Oct 24, 2008

Here is the site with the Yashica assembly diagrams. Hope it helps, good luck!

http://www-unix.oit.umass.edu/~coreya/yashica/ymchttc.html

paul ron · Oct 25, 2008

Is the replacement lens the same as the old lens?

The rear cell should just unscrew out n the new one put in it's place. Once you have it back together, there is a locking screw that keeps the viewing lens from turning in it's mount. It's just under teh top left side under the mounting plate. Loosen it. Now set up the camera on a tripod n aim it at a subject that will focus at infinity.

Mount a GG on the film plane of the open backed camera. Be sure it sits nicely on the film rails n tape it in place. Focus the camera, as if taking a pic, on the GG to that infinity sunject using a loupe to be sure it is razor sharp.

Now look into the WLF n see if it focuses properly? If not turn the viewing lens till it comes in nice n sharp. Set the locking screw n you are ready to fly. Oh be sure to check the close up focusing at min distance to be sure all is well.

Another site to look at with nice pics of the camera as it is being repaired... Dead Link Removed

A yahicamat is about the same shutter mounting...

Dead Link Removed

Ed Sukach · Oct 25, 2008

From many moons of lens testing, I'll say that elements are NOT interchangeable, Replacing one will degrade the overall performance of the system (read this as having a confidence level of 95%). It is POSSIBLE to "luck out" and improve things (in re-reading, 5% seem too optimistic), but I would NOT bet the farm on improvement.

Lens manufacturing tolerances necessary to insure element interchangeability would have to be fantastically "tight"; net result, one unreasonably expensive lens.

waynecrider · Oct 25, 2008

Thanks Paul for that information. I'll definitely give it a try.

Ed I hear you. The existing rear lens is bad, not possible to shoot at all. I thnk this is why the camera looks like new. I may as well try it and see what happens. If it turns out mediocre I'll try installing the other lens and go from there, but I appreciate you insight.

racer, thanks. Appreciate it.

ricksplace · Oct 26, 2008

Hi Wayne.

I have a Yashica D with Yashinon lenses. You don't say what is wrong with the rear element. The D I have had real bad fog on the rear element when I got it. I removed the rear element, and found that the fog was schmutz on the element, and cleaned right off. Unless the element is badly scratched, it may clean up nicely.

nuckabean · Dec 27, 2008

I've removed the rear element off my yashica mat without much difficulty using a small screwdriver.

waynecrider · Dec 28, 2008

nuckabean said:
I've removed the rear element off my yashica mat without much difficulty using a small screwdriver.

I guess you mean with an eyeglass screwdriver as the slots are very small.

Greg_E · Dec 28, 2008

There are a couple of things you can try.

Number one is a rubber stopper. Press it against the metal and twist.

If that fails you could try making a tool from some metal pipe and a file.

If that is too much work for something that may fail anyway, get the correct spanner tool from Micro Tools:
Dead Link Removed
or get them from ebay.

Needing to replace the rear lens on a TLR.

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