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glbeas
12-06-2007, 07:14 PM
I have a Zeiss Ikonta 6x9 folder acquired for a pocketable shooter for casual hiking. The shutter seized up so I opened it up to give it a clean and lube. That was successful, and I noticed the Tessar lens accomplished its focusing with a front element that moved while another element behind it was stationary. Makes me think this thing focuses like the human eye by changing the focal length rather than changing the lens to film distance.
Anybody know the story on this?

PHOTOTONE
12-12-2007, 10:28 AM
I don't know the theory behind it, but a lot of folding cameras used "front element focusing" and it seems this was an economy move, as the camera did not have to have the mechanics to move forward and backward the front standard. I would imagine front element focusing is a compromise in image quality over unit focusing.

Mustafa Umut Sarac
12-12-2007, 10:48 AM
Glbeas , can you post few pictures with your camera.

William Henry Jackson and Ansel Adams both used zeiss tessar at 35 mm.

I want to own the camera but money is in the sky with cubic zirconium ..

Ole
12-12-2007, 03:31 PM
It's basic photographic optics really - changing the spacing of a compound lens changes the focal length.

One early anastigmat, the Steinheil Unofocal (the name isn't as dreadful in German as it is in English), originally consisted of four airspaced lens elements where all four elements had exactly the same focal length, except that two of them were negative. Without spacing the focal length would have been infinity!

That's also how zoom lenses work, except that there are a few more elements to keep the mount-to-focal-plane distance (more or less) constant.

Mike Wilde
12-12-2007, 03:58 PM
http://www.zeiss.com/C125716F004E0776/0/3E640231096E4B6AC125717500672495/$File/Innovation_11_32.pdf
(http://www.zeiss.com/C125716F004E0776/0/3E640231096E4B6AC125717500672495/$File/Innovation_11_32.pdf)
I found this when researching my Ercona - the DDR similar version of the Ikonta

glbeas
12-12-2007, 04:16 PM
Thanks for the info, quite interesting.



Glbeas , can you post few pictures with your camera.

William Henry Jackson and Ansel Adams both used zeiss tessar at 35 mm.

I want to own the camera but money is in the sky with cubic zirconium ..

I've yet to get a good neg from it as a previous repair job had the focusing element in the wrong groove of the helicals and was misfocussing. I checked it with a ground glass when I reassembled to make sure it was right this time around. Next chore is to get my scanner functioning again so I can post images, something squirrely in XP has it shut down.