Absolutely,
and this is probably why it shows so good results right from wide open
(at APS-C bodies).
One more interesting fact. As you may know, there is a MTF sub-program
at K10D and K20D (actually the setting have been there since FA lenses
and Z/PZ bodies appeared - for example Z-1p has it). In this mode camera
tries to use the "sweetest" aperture range of attached lens. I do use it
quite often as my normal shooting mode and simply adjust aperture if I
don't like what camera likes (Hyper Program). Usually it means that
camera is trying to keep the aperture somewhere between f/5.6... f/8 or
so, but you never see any lens used wide open - even if there's no light
at all. Now, when I got DA*60-250 I was really surprised to notice, that
camera quite often decided to use f/4. I made a simple test and found
out, that in low(er) light situations (indoor at sunny day is enough)
K20D MTF program really chooses f/4 from 60-135mm and switches to
f/5...f/5.6 at longer focal lengths. Z-1p preferred f/5.6 through the
whole zoom range.
Isn't it a clear message from Pentax optical engineers - the lens is
really good enough to be used (at APS-C bodies) wide open?
BR, Margus
(and sorry for my muddy english)
Paul Stenquist wrote:
So that would suggest that perhaps the DA 60-250 was designed to be
used with both formats. That would certainly be a plus.
Paul
On May 11, 2009, at 10:39 AM, Margus Männik wrote:
Unfortunately DA*50-135 doesn't fit FF. Wide open you can see dark
corners clearly at 50mm, vignette achieves the maximum at 70mm and
then reduces to mild falloff after 90mm (but you can still see it at
135mm). Stopping down makes it worse and at small apertures you can
clearly see a round "imaging area" at all focal lengths.
BR, Margus
Paul Stenquist wrote:
True enough. I haven't tried my DA* 50-135 on full frame, but I
expect the results would be similar. I know the DA 50-200 covers
full frame. But if you believe Ned and the Pentax website, none of
these lenses were designed for full-frame use. As you point out, the
60-250 may be different in that regard. Or not. Some of those early
roadmaps were full of confusing nomenclature.
Paul
On May 11, 2009, at 9:45 AM, Mark Roberts wrote:
Paul Stenquist wrote:
Well, there you have it. Only minor vignetting. Would that
increase or
decrease at a smaller aperture?
It's probably falloff, rather than vignetting, and it would improve at
smaller apertures.
In any case, it's probably useable on full frame, although I would
think it's optimized for APS-C.
Since it was originally designated the "D-FA 60-250" I expect it was
designed for full-frame (they probably changed the designation to DA
when they decided to eliminate the aperture ring), but since virtually
all lenses show some light falloff at wide apertures and are sharper
in the center than the corners, any lens could be considered
"optimized for APS-C" :)
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