Lens design & glass types

[Dan Fromm]

Ian, it depends on the Tessar. My 1912 and, IIRC, 1936, 150/6.3s seem to be identical, details of mounting excepted. Both are in barrel. Arne and I discussed when the f/6.3s were redesigned, IIRC the design dates were 1903, 1911 (to improve ease of manufacture), and sometime post WWII for some but not all focal lengths. The original f/6.3 Tessar seems to have been right from the start, so very hard to improve.

There've been comments in this thread about redesigns due to availability (or not) of glasses. Maybe. Eric Beltrando once told me that the glasses that Boyer bought weren't exactly the same from batch to batch and that each design was tweaked lightly to suit the refractive index and dispersion of the new batches. He didn't see these as redesigns, rather as adaptation to variability in the materials used.

[Paul Fitzgerald]

" Worth
mentioning is also the 500 mm I.R. –
Tessar® f/5 lens for aerial photography
in the 30 x 30 cm format. "

What does the I.R. refer to? Infra-red maybe??

[IanG]

Dan, it would be interesting to know the break-down of Tessar production at Zeiss during the inter War years. I suspect that the 135mm outsold the 150mm in Europe as the 135's are much more common on 9x12 cameras. But I'd guess that sort of information is long lost.

That would then lead one to speculate if the 1928 re-design was to get improved coverage making use of the new optical glasses which had just become available.

Eric Beltrando once told me that the glasses that Boyer bought weren't exactly the same from batch to batch and that each design was tweaked lightly to suit the refractive index and dispersion of the new batches. He didn't see these as redesigns, rather as adaptation to variability in the materials used.

Those are names I haven't seen mentioned before, I'll have to remember where I read about the glass problem, I will have saved it somewhere.

ian

[Archphoto]

Paul, yes it could be that this lens was specialy made for IR photography and corrected for it.

Peter

[Dan Fromm]

Ian, see http://www.galerie-photo.com/boyer-o...-objectif.html and www.dioptrique.info

[Archphoto]

Thanks for posting these links, Dan, they are great.
Esp the last one gives a lot of insight into the development of photographic lenses.

Peter

[Paul Fitzgerald]

"Paul, yes it could be that this lens was specialy made for IR photography and corrected for it."

Thank you Peter, now I'll have to find some IR film and see if there is a difference in the focus spread.

For general reference, with a slight trim to the flange the 500/5 does fit onto a 6x6" lens board and mounts flush with the rear surface so it works with the built-in Packard shutter.

[Lynn Jones]

Thanks to CC Harrison,

I joined the original Calumet in 1964. We became the largest selling large format camera maker in the world (by 1967, 85% or a bit more of the VC cameras in the world). Quality lenses was our problem, American made Goerz had changed ownership 3 times and the quality was extremely variable. Schneider Symmars had some contrast problems and the shutters had sereious problems. One out of ever 5 lenses were failing at that time. Commercial Ektars, Wide Field Ektars and the portrait soft focus lenses sold well and stayed sold.

We received a message from Kodak that the professional lens division would be shut down in 1965. We bought lots of the warehouse stock and started looking for a new source. About this time a friend with a small investment group bought Ilex Optical. The president, our friend Manny Kiner agreed to make lenses for us with our name, Caltar. Manny studied the Commercial Ektar (tessars) and found that with some new optical glasses and computer re-design, we could make f 6.3 tessar type lenses of quality superior to Commercial Ektars. Within a year we were making and selling as many of our lenses as Schneider from our catalogs. Manny created a Super Wide 103 degree 90mm lens (Wide Field Caltar) which we put into Seikosha shutters followed by a 72 degree single convertible plasmat which we called the S Caltar. The S Caltar attracted so much attention that Rodenstock made a super deal for private labeling that particualr lens, although the 215mm f4.8 S. Caltar continued to be made for several more yers.

Manny had a terrible auto accident with such brain damage that he could no longer design lenses or work. Ilex over a period of 25 or so years eventually failed, but in the meantime B&J and BBOI made the same Ilex lenses under their own name as did Ilex as the original "Paragon" name. However, from the 1960's 'til the 1980's these lenses sold a huge percentage of LF lense under 4 different trade names.

The Calumet 4x5's (3 different models, one of which I created) and the 8x10's during the peak of production sold 12,500 to 13,000 cameras per year, internationally. The rest of the market was under 2,000 units.

Lynn

[Emmanuel BIGLER]

Ian, see ...

Daniel W. Fromm is so fluent in French that he forgot to mention the original English version of his invaluable article on Boyer lenses:
http://www.galerie-photo.com/boyer-lens-optic.html
"Traduttore, traditore !" Best to refer to the Urtext !

[IanG]

Thanks Emmanuel.

Ian