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09-05-2010, 10:52 AM   #31
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QuoteOriginally posted by hoojammyflip Quote
Asahiflex, thats a great portrait! Nice background and great light.

For what its worth, I've looked at the lens diagrams on Bojidar's Pentax website. I believe I am right in saying that the M 85mm was deliberately designed for portraits with a softer background with the older Takumar/Ernostar type confirguration, with less correction, than the SMC 85mm. In comparison, the FA 77mm has a Ultron Tronnier lens design, very similar to the exalted M 50mm f1.7. So, it depends what you intend to use the lens for. It seems to me from the old Pentax marketing literature (check out Pentax-manuals.com website), that the M 85mm was intended for portraits, whereas the FA 77mm is a more general usage lens. The other thing to bear in mind is that these were designed for 35mm full frame, and will bounce extra light around in the inside of a DSLR (someone should set about making some masks like that at the back of my M 200mm).
I think that this is a pretty fair assessment. in fact, I do feel the same that the M85 is great for portraits as well compared to the FA77.

09-05-2010, 11:41 AM   #32
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QuoteOriginally posted by hoojammyflip Quote
The Takumar 50/1.4 had the layout, designed even earlier than the A 85.


I find it very interesting that the same lens design can lead to different performances...I guess it comes down to the consistency and accuracy of the refractive index of the glass employed, the lens coatings, baffles, quality of the mounts for the elements, coatings...
The rear 2 elements were completely different in the A* and FA ltd though because they were 2 of the first lenses to incorporate Pentax's F.R.E.E. rear elements. They also added the Ghostless Coating to the LTD like they did the 43 ltd.

Edit: Actually, the 50/1.4 Tak started out with an 8 element design that was one of 3 high performance lenses that featured a cemented 3-element group that were eventually replace due to cost overrun.

50/1.4 8-element Super Tak


The Tak 83/1.9 still rivals any thing in that focal length by Pentax optically. The other was the Tak 58/2.

83/1.9






58/2

Last edited by Blue; 09-05-2010 at 11:56 AM.
09-05-2010, 12:49 PM   #33
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QuoteOriginally posted by Blue Quote
The Tak 83/1.9 still rivals any thing in that focal length by Pentax optically.
That front group looks like a Sonnar. What are FREE elements...is this something to do with the chemical make up of the glass. I'd be interested to know whether Pentax made glass for other manufacturers, and if so who. I understand that Zeiss lenses nowadays are in actual fact using Cosina glass....I guess the glass employed is very important and could also be expensive if using rare elements.
09-05-2010, 06:34 PM   #34
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QuoteOriginally posted by hoojammyflip Quote
That front group looks like a Sonnar. What are FREE elements...is this something to do with the chemical make up of the glass. I'd be interested to know whether Pentax made glass for other manufacturers, and if so who. I understand that Zeiss lenses nowadays are in actual fact using Cosina glass....I guess the glass employed is very important and could also be expensive if using rare elements.

The Pentax definition of FREE as per Dimitrov.

QuoteQuote:
Fixed Rear Element Extension (FREE): a lens with one or more optical groups that are physically fixed with respect to each other that remain fixed during focusing. FREE lenses achieve low field curvature with low spherical aberrations not only when focused close to infinity but also at very short distances. For normal applications the FREE system leads to small physical extensions, and thus allows the design of physically smaller and lighter lenses. For macro applications FREE lenses exhibit non-proportionately long extensions which aid precise focusing. However, to achieve these positive effects, the FREE design causes the lens focal length to decrease as the focus distance decreases.
As far as Zeiss using Cosina glass, I don't know. The small amounts of glass that Cosina melted was one of the limiting factors that Cosina had with their on designs. Leica and Zeiss had historically used glass blanks available on the world market and in some cases melted etc. to their specs.

Here is an interesting story on Asahi Optical's 85mm lens development history in context of the Sonnar etc.

Early Pentax Takumar Lenses

09-18-2010, 07:52 AM   #35
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Alright, my 77mm is on the way now
09-18-2010, 08:38 AM   #36
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Nice. I bet you are gonna love it. I wish I could afford one.

QuoteOriginally posted by yusuf Quote
Alright, my 77mm is on the way now
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