YashicaMat Yashinon and Yashikor lens elements

[Dan Daniel]

Just ran into an interesting situation with an older YashicaMat (LM model). The taking lens has a front ring labeled 'Yashinon.' I went to remove the rear group and the glass retaining ring came undone and I took the lens element out. On a Yashinon this should be a cemented doublet. But this is a single element, no joint.

The previous owner says that the images were always fine but not the sharpest.

My question is not about this particular camera per se or tracking down this mystery. I'm going to dig out some old cameras, look at the image quality, etc. in this sample. I'm more interested in-

Anyone know about the relation between Tessar-type lens designs and your basic triplet design like a Yashikor? Is a triplet rear element and a Tessar rear element similar enough to where the triplet element in the rear would generate an ok image? Is the Tessar formula based on using two elements in a cemented pair where there had been a single element before?

Well, any thoughts appreciated

 

[xkaes]

You might want to ask the experts over at the Yashica Board. That's where I go for Yashica/Tomioka/Kyocera info/advise. Tomioka made all of Yashica's glass.

https://yashica.boards.net/

 

[Dustin McAmera]

Paul Sokk showed that the lenses named Yashinon on the Yashica 44LM (the 127-film camera) are three-element. He describes how he examined the lenses, and also shows Yashica brochures saying they are three-element.

Yashica TLR Lenses & Shutters

Yashica Tri-Lausar, Yashimar, Yashikor, Lumaxar and Yashinon lenses and NKS, Y.S.K., Copal, Seikosha and Citizen shutters

yashicatlr.com

Maybe the full-size camera is the same.

 

[reddesert]

The history of the Tessar in for example the wikipedia page answers some of your questions: https://en.wikipedia.org/wiki/Tessar Basically, although the Tessar diagram looks a lot like a Cooke triplet with the rear singlet turned into a doublet, the two designs actually were derived independently from a common ancestor.

The designs are fairly similar in that if you swapped the rear element of one for another, it should make an image, but the aberration corrections would all be wrong. Lens designs have to be recomputed for the specific glasses available to the manufacturer, so that there is no single "Tessar" type, but a family of small variations. Meaning that even swapping the rear element of a Yashica Tessar-type with a different Tessar, say a Rollei or Mamiya Tessar-type of the same focal length, you would probably get a lens that focuses on-axis but has spherical aberration, and off-axis has astigmatism, coma, etc.

I have a Yashicamat EM, which is close to the LM, with a Yashinon lens. I looked at mine and the rear element is a doublet - you can tell by shining a flashlight in and looking for the faint reflection from the glass-glass interface (watch how the different reflections move in diff directions due to the curvature of the surfaces. Edit: There might be some Tessar variations where the surfaces have different curvature sign than the usual, I'm not sure).

 

[JPD]

The history of the Tessar in for example the wikipedia page answers some of your questions: https://en.wikipedia.org/wiki/Tessar Basically, although the Tessar diagram looks a lot like a Cooke triplet with the rear singlet turned into a doublet, the two designs actually were derived independently from a common ancestor.

The designs are fairly similar in that if you swapped the rear element of one for another, it should make an image, but the aberration corrections would all be wrong. Lens designs have to be recomputed for the specific glasses available to the manufacturer, so that there is no single "Tessar" type, but a family of small variations. Meaning that even swapping the rear element of a Yashica Tessar-type with a different Tessar, say a Rollei or Mamiya Tessar-type of the same focal length, you would probably get a lens that focuses on-axis but has spherical aberration, and off-axis has astigmatism, coma, etc.

I have a Yashicamat EM, which is close to the LM, with a Yashinon lens. I looked at mine and the rear element is a doublet - you can tell by shining a flashlight in and looking for the faint reflection from the glass-glass interface (watch how the different reflections move in diff directions due to the curvature of the surfaces. Edit: There might be some Tessar variations where the surfaces have different curvature sign than the usual, I'm not sure).

Yashinon isn't a design but a trade name, and many Yashinons are double gauss lenses, and a few were triplets. Apparently the Lumaxar lens on Yashica TLRs have the same design as the four element Yashinon and for some reason it was renamed Yashinon. And as said in the above posted article, some three element Yashinons have been found on Yashica 44 TLRs. It is confusing now when we expect that Yashinons on TLRs are four element Tessar-type lenses.

 

[Dan Daniel]

Thanks everyone. Great help as I look into this more.