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10-28-2009, 04:36 PM   #16
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I have no acces to a geiger counter anymore.

10-28-2009, 04:50 PM   #17
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QuoteOriginally posted by glasbak Quote
I have no acces to a geiger counter anymore.
That's too bad. You could get a baseline for the various 50s. I'll see if I can find one at work. I don't have any k series 50s though.
10-28-2009, 09:47 PM   #18
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QuoteOriginally posted by glasbak Quote
Looking at your forum name, I can't be supprised

I did not notice it either, but recently I acquired a 'Paterson Optical Test Target 2', and used it to compare various lenses.
From all the 50mm lenses I tested, I noticed a yellow cast in my white target for the K 1:1.4/50. Then I looked throug these lenses at a white surface, and these K 1.4 lenses clearly have a yellow cast.

George
Whatever you found on your K50/1.4 isn’t the same yellowing as is found on some Takumar lenses, the K series lenses did not use any Thorium elements.

Also Pentax changed the SMC process with the “K” series lenses and for the first time the seven layers were applied to most glass surfaces, including surfaces which are cemented together. Previously with the Takumar SMC lenses, some glass surfaces were single-coated.

I would love to see your K50/1.4 tested for radiation, please send it to “Blue”!! I’ll pay for the shipping.
10-29-2009, 07:50 AM   #19
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Hi to all.

K versio? S-M-C? SMC? A? FA?

I'm so confused. I found: Match 13: (2) SMC Takumar 1:1.4 50mm vs. (3) SMC Pentax-FA 1:1.4 50mm Photo Gallery by Sean Carpenter at pbase.com

Sure you know it, but there the S-M-C 1,4 is comparade to the FA 1,4. Conclusions?

I carry the images to my photoshop and crop to 200. No differrences I saw (only yellowish, a bit only, in S-M-C), and a narrow for the S-M-C.

The same lens over the time? Old lens a bit better at F/ 1,4 and F/8?

Help me to understand, please.

10-29-2009, 08:37 AM   #20
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estudleon,

Many people forget that the k series 50mm f1.4 is actually longer than the subsequent M, A, F and FA series f1.4 versions. While the element numbers, groups and designs are the same, the spacing is slightly different. The k lens is 42mm long and the later 4 lenses are 37mm long. The SMC formula may have been "improved" at different times during the 80s and/or 90s as well as 2000s. The number of coatings on the internal lenses may have been different as well. Another thing that gets over looked sometimes is that coatings can have tints to them.

Edit: I think there were changes made in the SMC coating for the M series 50mm and again when the A series 50 came out. I think the A, F, and FA had the same coating. Another subtle difference may have been the way that cemented group was coated and cemented and number of coatings on the internal elements as well.

The fact the Dimitrov lists the formula separately for the k, separately for the M and the A, F, FA reinforces my speculations.

http://kmp.bdimitrov.de/lenses/primes/normal/index.html

Last edited by Blue; 10-29-2009 at 08:56 AM.
10-29-2009, 03:22 PM   #21
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Thanks Blue.

The differents coating over the time is a reasonable thinking.

Rino.
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