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Pentax 3.5/15mm identical to Zeiss Distagon 3.5/15mm?
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PostPosted: Tue Mar 02, 2010 1:04 pm    Post subject: Pentax 3.5/15mm identical to Zeiss Distagon 3.5/15mm? Reply with quote

There have long been rumours about that, but mostly it was said that the Pentax superwide 3.5/15mm
is a inferior design compared to the famous Zeiss Distagon 3.5/15mm. My good friend Marco Cavina
worked long on that and finally found out about this secret here:
http://www.marcocavina.com/articoli_fotografici/15mm_Zeiss_Pentax/00_pag.htm

So looking a bit closer, the Pentax 3.5/15mm design by a "pure coincidence" (LOL) was also
from the hands of Prof Erhard Glatzel, ZEISS' design head in the 70ies!

Top shows the Pentax design, bottom Prof Glatzels patent paper ... coincidence?? I don't think so...
Pentax had contracted that development to Zeiss, since their own designers were not yet ready
for that complicated task.


(c) Marco Cavina


Last edited by kds315* on Wed Jan 02, 2013 5:23 pm; edited 1 time in total


PostPosted: Tue Mar 02, 2010 7:53 pm    Post subject: Reply with quote

Very interesting Klaus,
I've heard about this, perhaps Zeiss goal was to make more money out of such a elaborate design.
I would really like to see samples from the Pentax 3.5/15. The design seems to be identical and even the lens barrel, the hood, except the T* coating, of course.


PostPosted: Tue Mar 02, 2010 8:05 pm    Post subject: Reply with quote

Pentax got 15/3.5 design from Zeiss in exchange for 9-layer S-M-C coating formula (if I'm not mistaken)


PostPosted: Tue Mar 02, 2010 8:50 pm    Post subject: Reply with quote

This my Pentax 15mm lens:







PostPosted: Tue Mar 02, 2010 9:04 pm    Post subject: Reply with quote

Thanks for sharing Klaus! Yes, this is "common" knowledge about the Zeiss-Asahi connection, although I never saw definitive proof (until now). Thanks to this cooperation there also exists the SMC Pentax 1:2/28 (Zeiss Distagon 1:2/28 'Hollywood') and even the K-mount bayonet was designed by Zeiss. One should compare the Contax/Yashica mount with the K-mount and he will see the light Smile

By the way, you do not appear to have the version with aspherical element. It lacks the "4" feet marking on the focusing scale.

no-X wrote:
Pentax got 15/3.5 design from Zeiss in exchange for 9-layer S-M-C coating formula (if I'm not mistaken)


It was always said that the S-M-C process was invented by OCLI. I think this should be researched further. Personally I have the feeling that S-M-C was a joint development by Asahi and Zeiss.


PostPosted: Tue Mar 02, 2010 9:13 pm    Post subject: Reply with quote

There were two types for Pentax 3.5/15, the first one is aspherical element
used and the later one is spherical. Aspherical version has feet scale
is 7, 4, 2, 1.5 and spherical one has 7, 3, 2, 1.5 feet focusing scale.

The left one is the following photo is aspherical one. See>
http://www.ucatv.ne.jp/~tweety/SuperWide/K15/K15_35_j.htm

At Pentax making aspherical one was too expensive, later changed to
spherical one.

SMC TAKUMAR 1:3.5/15 for aspherical early version
smc PENTAX 1:3.5 15mm for spherical later version

I have no idea Zeiss one used aspherical element or not.

So Klaus' 3.5/15 is "spherical" one I guess.


Last edited by koji on Tue Mar 02, 2010 9:15 pm; edited 1 time in total


PostPosted: Tue Mar 02, 2010 9:13 pm    Post subject: Reply with quote

Yes this was Mr Glatzels genius to make the asph. element superfluous with a slightly modified design
and still keep the quality. Another proof that he was the father of that lens.


(c) Marco Cavina


Last edited by kds315* on Wed Jan 02, 2013 5:25 pm; edited 1 time in total


PostPosted: Wed Mar 03, 2010 1:13 pm    Post subject: Reply with quote

Spotmatic wrote:
Thanks for sharing Klaus! Yes, this is "common" knowledge about the Zeiss-Asahi connection, although I never saw definitive proof (until now). Thanks to this cooperation there also exists the SMC Pentax 1:2/28 (Zeiss Distagon 1:2/28 'Hollywood') and even the K-mount bayonet was designed by Zeiss. One should compare the Contax/Yashica mount with the K-mount and he will see the light Smile

By the way, you do not appear to have the version with aspherical element. It lacks the "4" feet marking on the focusing scale.

no-X wrote:
Pentax got 15/3.5 design from Zeiss in exchange for 9-layer S-M-C coating formula (if I'm not mistaken)


It was always said that the S-M-C process was invented by OCLI. I think this should be researched further. Personally I have the feeling that S-M-C was a joint development by Asahi and Zeiss.


Peter,

here is the study of the 2/28mm also confirming that it is identical to the Hollywood Distagon!
http://pentaxstudy.bufsiz.jp/Lensdesign/D28_20/D28_20_Design.htm