lens element swap between to yashica mats of different vintage
I posted about these yashica-mats before a half a year ago, but to reiterate: I have three 'Mats - an EM, 124, and 124g. The EM is currently a parts camera.
I discovered that my 124 was taking 'soft' negatives. Not soft like 'out of focus', but soft as in a lack of contrast. I took a look at the lenses and noticed what I thought was mild haze (that wasn't there before).
I took both elements out, and then discovered that it wasn't haze, but fungus on the rear element. I attempted to clean it but then wrecked it. (but I plan on keeping it for a future project).
Long story short: I replaced the rear element with the one that is from the EM, but noticed that the EM's rear element is different from the one on the 124, practically twice the length and probably of different formulation too. I'm not sure how I'm supposed to go about collumating it, I'm not sure if I should screw it in all the way like I would on the 124 series, or unscrew it out half way, or give up trying to pair a 124 front element with an EM rear and match it properly with the EM front.
Has anyone out there done this sort of thing? Any successes? Any weird effects?
Ummm.....yeah. For a TLR to focus properly, both lenses ( taking and viewing/focussing) need to be the same focal length. Your chances of hitting the correct focal length by mixing & matching lens parts are non-existant. Perhaps the lenses from the EM could be transplanted, but they will almost certainly need to be shimmed so they track properly.
Sorry for my absence.
Anyway, I should have mentioned that both taking lens sets are Yashinons, not Yashikors or Lumaxars. My viewing lenses are 80mm Yashinon f/2.8's , and I'm not mucking with that!
I have the rear EM cell already screwed in, same threading and pitch. I'm hoping I won't have to shim anything, the only thing that is unsettling is that the EM taking rear cell is almost twice the length screwhousing wise, and and probably more glass (I'm not sure.). I'm hoping that someone has done this before and knows of the results. But for tonight, I'm matching both front and rear EM cells, I'm not ready for potential weirdness.
It's kind of amazing what difference 4 years can make in specifications.
Swapping elements between lenses from different models is not a good idea. Even though the lenses may have the same name and specifications there may be differences in the formula. Once you determined that the rear elements were different you should have quit. Disassembling lenses is best left to a professional.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.
~Antoine de Saint-Exupery
And, even if the glass is "identical", there's no guarantee the spacing of the cells in the shutter is the same. Once again, the taking lens must match the viewing lens.... the two lenses were originally selected to match each other within tolerance. The fact that you've trashed one lens already due to improper cleaning should tell you something. Good luck...you'll need some.
Originally Posted by Gerald C Koch
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Only one way to find out!
Yes, use a micrometer to ascertain that the shutter spacing is the same, and check the focus with a ground glass at the film plane, shimming things if neccesary to get focus to coincide. Simple, if you a) know how, and b) have the tools.
Originally Posted by Steve Smith
OK, two ways!
Do it then expose some film.
Well, I'm back with some good news. I've decided to go 124 front with EM rear, and I was able to get the rear element dialed in the way that I want it and ascertain sharp center and off center focus and have it match with the viewing lens. I have not been able to determine if I have serious light fall off at f/3.5. I did a quick comparison with my 124g and ground glass, and it seems almost the same, but I only spent a minute at most checking. I've been (unexpectedly) rather busy and I was roped into taking care of a friends' dog that is amazingly needy and mischievous at the same time. Combine that with my dog and it's total chaos.
At the rate this is going, I might not have to shim the lens board to compensate. I have done this before, if you're willing to search you'll find my first thread regarding my Yashicamats asking about shims (I called them washers, but same thing). And with regards to the wrecked 124 rear element -it's not that wrecked, before I bought the camera someone must have (inadvertently) stripped part of the coating on the outer edge, (probably) combating the same fungus. All I did was make it worse. It was either try it or find another exact donor camera, or spare front and rear groups. No biggie, really, like I said before it could be an interesting softening gimmick for a future project.
I wanted to use the EM front, but as the saying goes - "Spec. changes all the time, without warning". I'm not perfectly knowledgeable about EM's (mine was made in 1964), but either
A. The front name plate ring stripped from the rest of the lens housing (the part that says "Yashinon f/3.5 [some serial number]"), freeing the first glass piece from the surly bondage of professional abuse.
B. The front group was assembled piece by piece into a shutter, never meant to be disassembled, Which leaves me wondering how the other two elements in their housing got screwed into the shutter in the first place.
I'm sticking with A. It's kind of a shame, but the EM camera was destined for the dumpster (it was literally a "take my wife, please" kind of deal, it was that hopeless, and I used that camera as a learning experience. When I bought all three of them, none of them were functional, and I put a lot of effort into the 124's to get them functional. None of my work is contingent on them functioning, and I'm not trying to sucker someone by flipping. I do plan on keeping them. Also, I would never DIY repair a Rolleiflex or Hasselblad, only Yashicas and lesser cameras. So let's not get too upset over this.).
I have a roll of HP5 for it, I'll clue you all in a month from now in the future if it is successful (I'm backlogged). I do recognize that I am going where no man has gone before (and lived to tell the internet), that's why I made this thread.
/I wish I hadn't noticed my to/two mistake in my title. ugh!