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10-13-2012, 02:31 PM   #1
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Lessons from a Legendary Lens Designer

This starts out to be another rehash of Mike Johnson's 10 year old paper on the "Best Lens". However, he pivots on a dime and does a partial re-translation of Jun HIrakawa paper on the design of the limiteds....



10-13-2012, 02:43 PM   #2
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Interesting read. I would like to see a better translation of that paper, though, and not just a re-interpretation of the bad translation.
I think Pentax should do some more lenses like that for digital.
10-13-2012, 02:47 PM   #3
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Thanks for sharing. This is a very good article and explains much of why the 77 limited behaves the way it does.


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10-13-2012, 03:57 PM   #4
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Pixie dust is unquantifiable by pixel peepers - till you understand that, till you move beyond numbers and tests, until then the FA Limiteds will always remain an enigma, when you do, they become objects of awe.

10-13-2012, 06:13 PM   #5
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It would still be interesting to read what was going through the minds of the creators of the FA31 limited - they had to make a lens that would fit in with the optical qualities that are shared by the first limited lenses designed by Jun HIrakawa - no easy task.

From what I have seen the FA31 has a rendering that is different in subtle ways from the FA77 and the FA43 limited, it is contrasty yet delivers superb corner to corner resolution on FF - yet it has aberrations, but they are controlled by the inclusion of ED, HRLD, and Aspherical lens elements, which counter many optical flaws that are common with wide-angle retro-focus designs. Although the FA31 scores exceedingly well at numerical testing and offers performance that is capable of matching and in some cases, exceeding lenses costing well over three times the price.
10-13-2012, 06:28 PM   #6
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From what I've read, Hirakawa-san wanted the FA31 to take a different, slightly smaller shape with a different optical formula. Not sure how factual that is, but I suspect that there are more than a few brilliant minds in the Pentax stable.
10-13-2012, 06:33 PM   #7
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Sadly the one of the FA31 creator has gone to Nikon...
10-13-2012, 07:05 PM   #8
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QuoteOriginally posted by gtl Quote
Sadly the one of the FA31 creator has gone to Nikon...
No, Canon.

10-13-2012, 07:07 PM   #9
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I have the original paper somewhere in the house . . .
10-14-2012, 12:41 AM   #10
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QuoteOriginally posted by interested_observer Quote
This starts out to be another rehash of Mike Johnson's 10 year old paper on the "Best Lens". However, he pivots on a dime and does a partial re-translation of Jun HIrakawa paper on the design of the limiteds....
The author is one of our active forum members:

northcoastgreg - View Profile - PentaxForums.com
10-14-2012, 12:59 AM   #11
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QuoteOriginally posted by Digitalis Quote
they are controlled by the inclusion of ED, HRLD, and Aspherical lens elements
HRLD = high refraction low dispersion?

Last edited by lytrytyr; 10-14-2012 at 02:34 AM. Reason: Correcting typo "diffraction"
10-14-2012, 02:24 AM   #12
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QuoteOriginally posted by lytrytyr Quote
HRLD = high diffraction low dispersion?
According to my Schott glass catalogue it is probably High Refraction Low Dispersion glass like SCHOTT LASF2 or HOYA TAFD55 - they called it HRLD as a marketing thing...manufacturers don't actually tell us what glass types are used in their lenses, for optics geeks like me it would be utterly fascinating if they did.

Last edited by Digitalis; 10-14-2012 at 02:37 AM.
10-14-2012, 02:39 AM   #13
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This one:

http://www.hoya-opticalworld.com/common/pdf/TAFD55.pdf
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