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09-13-2012, 05:32 PM   #16
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QuoteOriginally posted by Lowell Goudge Quote
I just hope that it delivers performance, and for me, that means close focus of less than 2.5 meters
MFD is 5.6m, as per PENTAX - HD PENTAX DA 560mm F5.6ED AW

09-13-2012, 06:11 PM   #17
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I think Pentax is pretty messed up on this lens. They have marketing photos with "SMC" graphics for this lens but it is listed in their official website as one of the new "HD" lenses. Someone asked on facebook which it was and got marketing speak on how great HD is, which is fine but it still raises the question of why "SMC" was put on those marketing photos??? As for longer, telescope designs being cheaper to make - wow! What would a compact 560mm from Pentax cost?
09-13-2012, 07:47 PM   #18
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It will be interesting to see how the lens testers like DxO and photozone test this lens for maximum image quality, as it's optimized for distant subjects.

Not a lot of point in using their usual indoor test charts, methinks. But I wouldn't be surprised if they try... and stupidly hammer the lens quality because of flawed testing.

Some moonshot comparisons would be a good way of doing it, I wonder if the Apollo astronauts remembered to leave any resolving power charts there with the laser reflector?
09-13-2012, 11:42 PM   #19
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Without having it in hand my take on it:

It is essentially a 560mm prime focus telescope with the addition of auto focus and auto diaphragm.
The main objective is a 100mm three element "APO" ED glass and the other elements are only there to allow internal focus.

It is not a true "telephoto" in the sense we use the term in photography. The Sigma 500mm for instance. The Sigma has
an additional negative focus group as a rear group that is essentially a built in TC. This allows for a shorter physical length
but is not a true prime focus 500mm glass but gives an "apparent" focal length of 500mm. Nor is the Sigma a true telescope.

Notice what we call a "telephoto" in photography that it's true physical length is never anywhere near the stated focal length given. That's because its apparent focal length not the actual true physical focal length (prime focus). The "500mm" Sigma's actual physical length is 350mm for instance.

On the other hand this scope's actual physical length is 520mm + registration distance = 560mm

Just my best guess.


Last edited by wildman; 09-14-2012 at 01:53 AM.
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