According to Boz, the DA* 200mm 2.8 and the FA* 200mm 2.8 have the same
filter size, dimensions, number of elements and groups, and minimum
focusing distance. Well, that's one possible case of one still available
DA* lens capable of printing the entire 35mm frame, even if only marginally.
Or a Full 35mm Frame lens ready as soon as they discover the need - wich
they won't, as long as we understand Corporate Pentax's ideas for the
future.
Still looking for hands on results. :-)
LF
Luiz Felipe escreveu:
As long as I agree there is little sense in working an APS-C lens with
35mm image coverage if you don't want your lens to be used on 35mm, I
don't believe they would take pains to restrict the image circle if the
lens design came from a 35mm version. Flare control baffles could
possibly be enhanced and the reduction on the original image area
accepted. But other than that the lens could be still be able to print
35mm. Not a proper design from the ground, but some revision of an
existing and proved successful one. Possible case of the DA* 200mm 2.8??
I'll be doing some spec reading at Boz' pages tonight.
Anyway my question did assume greater lens availability from Pentax.
Since the only DA* lenses available with long reach into the 135~200mm
and 2.8 aperture are the 50~135 and the 200mm, I really should ask if
any 35mm film users ever tried those lenses on anything but APS-C
Pentaxes, and what results they got. It's all about getting more uses
for Pentax lenses, after all.
LF
JC OConnell escreveu:
The other thing to note is well designed lenses for a specific
format (like APS format and DA lenses)many times could optically
work but because they are designed for smaller formats may have
good baffling and front rings that will vignette if used on a larger
format like FF.
JC O'Connell (mailto:hifis...@gate.net)
"Honesty is the first chapter in the book of wisdom" - Thomas Jefferson
-----Original Message-----
From: pdml-boun...@pdml.net [mailto:pdml-boun...@pdml.net] On Behalf Of
John Francis
Sent: Wednesday, April 29, 2009 1:09 PM
To: Pentax-Discuss Mail List
Subject: Re: image circle of DA lenses: how much smaller than FF?
On Wed, Apr 29, 2009 at 01:35:09PM -0300, Luiz Felipe wrote:
I was looking for data on the available 180~200mm 2.8 lenses for K and
EF mounts, and found some story about how the DA* 200 2.8 is related
to
the former 200mm full frame and so it possibly would cover said full
frame.
That got me wondering if one of the tech-oriented actually knows the
image circle dimensions for the DA lenses, and how much is missing. I
know the difference should be proportional to the difference from
APS-C
to 24x36mm, but would like ko know the size and borderline falloff
evolution on the DA lenses.
Just wondering, TIA. :-)
LF
Above some focal length (well below 200mm) it's likely that just about
any lens will have an image circle easily large enough to cover 36x24mm.
But, as Ned Bunnell point out in his blog entry on the forthcoming
camera, there's a difference between covering an image circle and
covering it well. The DA lenses are not designed for sensors of that
size, so things such as corner resolution, distortion, etc. may not be
sufficiently high. (There again, as he also mentions, some older lenses
may also fall short in that regard, even though they were designed for
use on film cameras).
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Luiz Felipe
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http://techmit.com.br/luizfelipe/
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