I am talking about the first generation of the 180mm, 240mm and 270mm f/5.5 Schneider Tele-Artons from the 1950's (the 360mm was not available those days; it came only with the second generation of the line, the Tele-Gauss one. I was never interested in the Tele-Gauss type Tele-Artons and actually know nothing about them). The first ones had a biconcave element at the very front followed by a negative lens element quite close to the first one; they are easily recognized by a relatively small front cell and a larger rear cell behind the shutter. The later Tele-Gauss type Tele-Artons have bigger front parts and much smaller rear ones. According to the serial numbers I've seen on that auction site, the transition should have been made in about 1964.
I paid my attention to the first-generation Tele-Artons because I wanted to try unscrewing the front element a little bit just the same way many of us do with Heliars, Tessars, Celors and Triplets. That gives a soft-focus effect (which I don't want usually) and also improves the background blur (which I am actually after). Tele-Gauss (as well as Double-Gauss, Sonnar type and many other) lenses are not prone to the effect; but some other type telephoto lenses do. For example, I've successfully unscrewed the front of the Mamiya TLA Sekor 180mm f/4.5 Super two full turns to make its ugly OOF background into a pleasant one; though that lens lost sharpness quite a bit and became especially bad in its chromatic aberration - but still OK in the center and thus quite usable on small format SLRs. (With lenses not made to be adjustable by moving their elements I just unscrew the front 'nameplate' ring, apply some elastic cement on the back of it and screw it back in. When the cement sets, screwing the front metal ring forth and back makes the front glass element to move along while not going off axis.)
So that was what I did to my 180mm first-generation Tele-Arton. Instead of about two front ring turns I was accustomed to with tessars, just 1/4 of a turn was enough to make me happy with the Tele-Arton's image at full aperture. And I liked the image I got much more then the ones I get with any of the tessar-type lenses. (Again, I am not after the soft focus effect. In fact, I am the most happy if I get a nice out of focus background rendition with still no softness in the image. But I guess other people can just go moving the front lens element further and further....) The focal length change with the front element thus moved was negligible - just no more then a millimeter perhaps (my Sekor 180mm f/4.5 Super became about 172mm when unscrewed its two turns, and the focal length change in Tessars, Heliars, etc., etc. is well known also). The loss of sharpness wasn't too easy to see, too.
Then I bought the 270mm f/5.5 Tele-Arton of the same generation. It was nice.... but positively yellow-brownish. While the 180mm had just a bit of amber tint very pleasant in color photography and not too much of a trouble even for blue-sensitive BW film, the tint in the 270mm was way too much. I suspected Thorium glass was at play but my internet research gave no data on Thorium in Tele-Artons. Nevertheless, the color shade was so similar to that of my Kodak Color Printing Ektars....
I borrowed a nail varnish UV curing box from a kind girl, and under its 4 x 9W BL-type fluorescent lamps both Tele-Artons (and a Color Printing Ektar, too) perfectly cleared in 62 hours. In fact, they may actually have been clear much earlier but I just went away for a weekend and did not check the glass until Monday.
And the last but not least.... In modern terminology, those first generation Tele-Artons would be certainly called APO's. Those days the prefix was not used that freely but Thorium glass did the trick. Chromatic aberration is extremely low in the 1950's Tele-Artons, and it does not increase when the front element is moved a bit forward.
.... Hope this helps somebody.
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Originally Posted by Corran
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