[Leica] Zeiss ZM 21 & CornerFix

[roark.paul at gmail.com (Paul Roark)]

Mark Rabiner <mark at rabinergroup.com> wrote:
> ...
> Center filters is what symmetric glass are said to need and there's been a
> cottage industry making them for decades for all the finest lens
> manufacturers making symmetrical lenses notably the German ones Rodenstock
> and Schneider (JSK) for view cameras.

All that I've seen so far are too large for the 21mm Biogon (46mm
filter size).  Ideally, I agree that would be the best way to deal
with light fall-off, but in practice, I think I'll end up relying on
CornerFix and possibly multiple exposures.

So far, the increased noise in the skies near the edges and corners
has been the main visible artifact.  Increasing the ACR noise
reduction -- color and luminance -- in a second "development" of the
DNG has given me the smoothness needed to deal with the noise.  (I
don't use any luminance and restrict even color noise reduction in the
main DNG conversion to avoid softening of details.)

Paul
www.PaulRoark.com




> Though a modern retrofocal lens like the 21mm f2.8 Elmarit M ASPH is so 
> well
> corrected after years of computer design that they almost emulate a true
> wide angle lens like a Biogon or SA. But I think almost not quite as far as
> correction goes say for architectural use a symmetric is the lens of 
> choice.
> And its a shame the are monsters which weigh a ton comparatively.
> But gee there is no fall off an the edges.
> Me I'd buy a center filler which gave you fall off on the edges as I darken
> the edges on every image I ever make first in the darkroom and now digital.
>
> Sheet shooters love a Biogon or super Angulon with their amazing low 
> profile
> compactness and don't mind the amazing lack of distortion at all.
> Witness the amazing history of SA use on Leica M.
> There have been more than a few shooters who shoot Leica M only for that
> reason. A few on the White House staff. With a nikon with a 105 on one
> shoulder and a Leica M4 with a 21 3.4 SA on the other.
> I've yet to score one I borrowed a modern Hassy superwide for a week and 
> did
> lots of shooting with it. Much of it on a tripod with the camera carefully
> leveled. And at f11 with everything zone focused from 3 feet to infinity.
> I'll love it when I can work with a true wide again. As in own one.
>
> --
> Mark R.
> http://gallery.leica-users.org/v/lugalrabs/winterdays/
>
>
>> From: Paul Roark <roark.paul at gmail.com>
>> Reply-To: Leica Users Group <lug at leica-users.org>
>> Date: Sun, 15 Jan 2012 08:31:07 -0800
>> To: Leica Users Group <lug at leica-users.org>
>> Subject: Re: [Leica] Zeiss ZM 21 & CornerFix
>>
>>>> LR apparently has a built in vignetting fixer in its later versions. 
>>>> ?Does
>>>> LR now negate the use of Cornerfix?
>
>
> It's possible that CornerFix is
>>>> superior to even Leica's lens-coding
> profiles. ?It is custom for each lens
>>>> and body. ?You could even make
> it custom for each aperture if you wanted.
>>>> Canned profiles may be
> less accurate for your particular setup.
>
> Actually,
>>>> the issue with the 21mm Biogon is that it's a symmetrical
> design -- said to
>>>> be terrible with the M9, with a nodal point that is
> way too close to the
>>>> sensor. ?But symmetrical designs are, in my view,
> superior in terms of
>>>> sharpness and distortion to retro-focus. ?The 21
> Biogon is really sharp,
>>>> with no distortion. ? My 18mm Distagon, said
> by some reviewers to be the
>>>> best 18, is good, but not up to the
> Biogon. ?For making large prints, I was
>>>> a bit disappointed in the 18,
> thus the 21 Biogon experiment, which luckily
>>>> worked. ?But for
> ColorFix, I probably would have returned the Biogon as
>>>> unusable with
> the
>>>> M9.
>
> Paul
> www.PaulRoark.com
>
> _______________________________________________
>>>>
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>>>> information
>
>
>
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