1958 Yashica 35 - The Time Machine

[Ernst Dinkla]

To start with the last request: It is the Mamiya 35S with the Mamiya Sekor 48mm 1.9 that has basically the shape of Plasmat lens. There are more Mamiya 35 cameras with that lens design, I suspect that both the 48mm 2.0 and 1.9 of the fixed lens rangefinders have that design.

The Minolta 35 B for example: Chiyoko 45mm 1:2.8 tests and review - Lens QA Works however the lens is a 5 element 3 groups, my mistake. The fixed lens rangefinder Minolta A2 with the 45mm 2.8 has the same design.
The Ricoh 35 De Luxe with Riken Ricomat 4,5cm 2.8 also shows the same 5 element 3 groups design.

 

[Ernst Dinkla]

BTW. The Fujicaflex TLR 6x6 camera uses the same 5:3 optical design for its 83mm taking lens.

 

[TenEleven]

BTW. The Fujicaflex TLR 6x6 camera uses the same 5:3 optical design for its 83mm taking lens.

And viewing lens as well. The lenses are identical. (Well I assume they used lenses which did not quite make the cut for the viewers.)

I assume to facilitate the close up mechanism which works by rotating the cemented front element, extending it out akin to a camera with a front cell focusing lens.

 

[Ernst Dinkla]

And viewing lens as well. The lenses are identical. (Well I assume they used lenses which did not quite make the cut for the viewers.)

I assume to facilitate the close up mechanism which works by rotating the cemented front element, extending it out akin to a camera with a front cell focusing lens.

Interesting. So for the normal range unit focusing is used and then for nearby front cell focusing. Increasing SA by that but while an abberation it could compensate the reduced DOF at nearby. At least give that impression.
This lens type is not free from astigmatism either according: M42 MOUNT SPIRAL

 

[TenEleven]

It would not surprise me if there was some residual astigmatism. There is also residual spherical aberration that gives the images their pleasing gentle look.

I think that the square nature of the 6x6 negative will however spare you from the worst.
Similar story for the vignette.

Edit/addendum: The feature is more of a gimmick to me anyways, at the close range it offers you are severely bound by parallax, which unlike Rollei's solution this does not correct for in combination with the extremely shallow depth of field you already pointed out. This means that trying to recompose (hand held even at f/5.6 or so) to compensate for parallax is going to greatly reduce the chance of the image being in focus.

That all said, Fuji's lens designers surprisingly placed little value on fully eliminating astigmatism for some reason. Even their "headliner" 50/1.2 has some of it.

This is doubly surprising because it is a Sonnar type lens and Sonnar lenses, from what I know (as an amateur at least), are relatively easy to correct for astigmatism. It was supposedly one of the desirable traits of the design over the competition which required more effort to eliminate or reduce it.