Archived posting to the Leica Users Group, 2000/09/07

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Subject: [Leica] Voigtlander 12mm lens
From: Jem Kime <jem.kime@cwcom.net>
Date: Thu, 7 Sep 2000 12:14:13 +0100

...was reviewed for the first time in a British magazine published 
yesterday.

Roger Hicks informed British Journal of Photography readers over a two page 
spread that essentialy the lens was very good indeed.
Although he acknowledges that resolution tests are far from conclusive he 
wrote:

"For resolution testing (on Ilford 100 Delta) the camera was a mere 60cm 
from the test charts. The targets used were the old Polysales types that 
are relatively low in contrast, about 32:1 (1.5 log density range), and 
giving a direct reading in lpmm when photographed at 50x the focal length, 
hence the 60cm distance.
The resolution figures are clearly of limited relavence in any absolute 
sense being partly subjective and also affected by film choice, development 
conditions, subject contrast and more. But even so, the readings obtained
(f5.6 	100/65++
f8	100/65++
f11	100/65++
f16	80/65
f22	65+/50+)
are impressive by abny standard, for any lens film combination.
The recorded 100 lpmm on the film wide open is as good as anyone could 
expect, and 65++ (a very easy 65lpmm) could easily be 80- (80lpmm with a 
bit of optimism). With a lens having this angle of coverage, such figures 
defy belief
The lens is at its best from wide open to f8, deteriorating very slightly 
from f11 or so and rapidly thereafter: the only reason to use f22 is for 
trick shgts with extreme depth of field."

Much of the text details the facts that can be grasped from the technical 
data released so far but he does amplify his tests with some judgements on 
performance.

"In real world use flare is far lower than it has any right to be and 
curvilinear distortion is simply negligible. Coma too is extremely well 
controlled. [...] Equally inevitably there is some vignetting and even 
though the designer seems to have made use of the Slussarev effect* to 
reduce it, with such an extreme angle of view it is detectable. Often the 
pictorial effect is actually attractive."

He goes on to conclude that the main drawback is that of accurate framing 
resulting from the non-reflex mode of working. Close foreground detail can 
often be quite different between the viewfinder and the lens's viewpoint. 
Whereas the Voigtlander has the accessory shoe directly above the lens 
mount, we Leica users will have to move the camera both upwards and 
sideways to achieve the same framing seen through the finder.

(c) BJP 06/09/00

Jem
* Having tried to locate a definition of the Slussarev effect, I sadly 
can't. Can anyone elucidate?