Some of the digital fringing I've seen appears to be something other
than conventional CA. And yes, I've seen it in the middle of the frame
with the A400/5.6. ACR's CA correction doesn't seem to affect it. The
only fix is color replacement and careful cloning.
Paul
On May 28, 2009, at 7:27 AM, J.C. O'Connell wrote:
I don’t know what that was, but the common CA problem is
NEVER right down the middle. It’s a different size image
Vs wavelength such that you end up with different focal
Lengths vs wavelength. The symptom is you have three images
Coaxial to each other with ZERO fringing in the center,and
Maximum fringing at the corners. So if you were seeing some
Kind of problem in the center of the image It was not typical
CA problem, must have been some other rare problem.
J.C. O'Connell ( mailto:[email protected] )
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of
Brendan MacRae
Sent: Wednesday, May 27, 2009 11:02 PM
To: Pentax-Discuss Mail List
Subject: Re: Big-telephoto advice
The A400 5.6 suffers pretty bad CA even right down the middle, at
least
mine does. There was a long thread about this a couple of years ago
when
I posted a shot where the fringing was pretty bad in the middle of the
image and the scene wasn't even backlit. The CA correction in Camera
Raw
and other converters can't fix it.
That was coupled with the K10D. I've not used it much with the K20D.
----- Original Message ----
From: paul stenquist <[email protected]>
To: Pentax-Discuss Mail List <[email protected]>
Sent: Wednesday, May 27, 2009 5:53:44 PM
Subject: Re: Big-telephoto advice
The A 400/5.6 is a much better lens than the screwmount, the SMC or
the
M versions of the 400, in that it will focus close enough to get a
bird
full frame, and it gives you all metering options on a Pentax digital
DSLR. I've seen them for less than $400. I think that's about what I
paid for mine four or five years ago. A decent lens. It also works
well
with the Pentax AX-S 2 and 1.4 converters. It doesn't accept the L
converters. Some CA on digital cameras when shooting branches against
the sky, but that's fixable. I would guess the SMC 500/4.5 or 300/4
are
even worse in that regard. Paul On May 27, 2009, at 8:28 PM, Tim Bray
wrote:
On Wed, May 27, 2009 at 5:25 PM, Bob Sullivan <[email protected]>
wrote:
Tim,
A screwmount SMC Pentax 300mm f4 or 400mm f5.6 would be great. Most
everyone else passes on these as too old, their problem!
Those 300 screwmounts (under the Takumar name, right?) are all over
the place in the non-SMC version, harder to find with the SMC. How
big a deal is the coating? -Tim
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