Med Format Collection

[Thomas78]

Oh, by the way, the Record III was able to accommodate a much bulkier lens (Ross Xpres) (with just a little work) than the f/4.5 Apotar, I think it would be the same for all Record models of that time 🙂.

This is a very nice conversion and combines a very light and compact camera body with a (as far as i have read) very good lens.
Btw. my Record II with Apotar is about 690 g and by far my lightest folder in 6x9.

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>>Roland Haid , Apr 04, 2003; 02:34 a.m.
Dear Ernst,

according to J. Stüper, Photographische Kamera, 1962, a lens with front focusing is designed to have optimum performance at a distance of 40x focus_length, hence 2m for an 50mm Triplett or approx. 4m for a 6x9 camera. Thus, good performance for such a design is then provided between 20x focus_length and infinity. If a Tessar design is set to 4m and fixed then, the quality will be much the same for far distances, because Tessar's are robust in variation in object distance.

On the other hand, a lens with front focusing which is optimised for 40x focus_length the spherical aberration will be overcorrected for far distances, this is not a problem because for landscape photographie the lens is used with smaller stops most times and the increase is small. If you fix the front lens at infinity setting, the overcorrected spherical is (not exactly) fixed for all distances and subsequently reducing the quality. Best regards, <<

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Ernst

Thank you for the interesting note!
Could you please explain the highlighted sentence?
Is it related to the spherical aberration which you mention in the next paragraph?

 

[Ernst Dinkla]

Could you please explain the highlighted sentence?
Is it related to the spherical aberration which you mention in the next paragraph?

My question then was: If I use a front cell focusing Tessar on a camera that focuses with the total lens on what distance should I fixate the front cell to get an optimal quality? That relates to: At what distance is a front cell focusing Tessar about equal to a normal Tessar?

The two answers suggest that you can not get spherical abberation correct if optimal quality (resolution) is found and the other way around. I could live with the overcorrected spherical abberation in that case.

For the tinkering this time the front cell focusing is not fixated but the basic focal length is slightly increased with the front cell. Front cell focusing is a kind of primitive zoom function, the focal length of the lens changes instead of moving the total lens to get focus.

Ernst

 

[Thomas78]

Thank you Ernst!

Perhaps the problem with sperical correction ist one of the reasons why Zeiss choose a minimum focus distance of 1.5 m at their Super Ikonta C.


FYI I started a smiliar thread at the Optics&Lenses Subforum recently:

Tessar (type and triplet) front element focusing - focus shift

 

[Ernst Dinkla]

This is a very nice conversion and combines a very light and compact camera body with a (as far as i have read) very good lens.
Btw. my Record II with Apotar is about 690 g and by far my lightest folder in 6x9.

The Anastigmat Special lens is transferred to the Record but not yet calibrated for distances. 677 grams in total I measured. The shutter coupling works too now including the prevention of double exposure, better than ever on the Monitor. For folding I have to cock the shutter first which is not ideal.

Ernst