[Leica] Focotar report

["Anderson, Ferrel E" <AndersonF@ria.army.mil>]

Erwin,

Very interesting.  Your assessment of the 40mm Focotar is in line with what I
have been able to determine for my 40mm Focotar with my Four Seasons resolution
slide and my Omega grain magnifier.  I am not confident in the resolution
results I achieved on the far edge since I had to tip the magnifier to even see
the image, and I had no ability to determine the resolution in the corners.  I
am reduced to making prints of the positive to make a final determination, and
this is really the proof-of-the pudding test.  How did you determine resolution
across the field?

One must realize that your test pitted the 40mm Focotar, which is a wide angle
lens, against a 50mm focal length normal lens that is  easier to design.  It is
also an APO lens and is more recently designed and computed than the "older"
Focotar.  A fairer test would be to determine how the Focotar stacks up against
another wide angle lens such as the Schneider 40mm APO Componon HM.  This would
be a more appropriate test.  Also, how does the 50mm f2.8 Apo Rodenstock stack
up against the Leica 50mm f4.5 Focotar-2 lens?  My test of this lens resulted in
performance very close to what you report for the Rodenstock lens.  This last
comparison is what I would like to see from you.  

I am planning to test my 40mm Focotar against my 50mm Focotar-2 lens on my V35
enlarger later this fall to see what the practical differences there are at
various apertures at  magnifications of 5X, 8X, 11X, 16X and 20X.  I might even
try 30X.   I will also try to get samples of the Schneider and Rodenstock lenses
discussed above to include in the tests.

Ctein, in his various discussions about enlarging lenses in Photo Techniques and
Camera and Darkroom magazines, states that the tonality of a print is to a large
extent determined by whether the enlarging lens can resolve the grain of the
image.  He maintains that in order to accomplish this, the lens must resolve
over 200 l/mm (100 lp/mm), and preferably at least 250 l/mm (125 lp/mm).  This
level of resolution can only be achieved in lenses at f5.6 and larger apertures
because of diffraction affects which degrade performance  at f8 and smaller
apertures.  Yet Leica in their literature state the best aperture of the Leica
enlarging lenses is f8.  Any discussion on this from you LUGers?

Just a note to add to the subject.  In the Modern Photography test of the V35
enlarger, they stated that the performance of the 40mm Focotar was the best they
had ever seen with the exception of the $1,600 100 APO enlarging lens (no doubt
the APO El Nikor) in testing with their test color negative.  Theirs was a
practical test.  

Too bad Leica has walked away from the enlarger product line.  At the least,
though, they should come out with some new enlarger lens designs that will
support the autofocus capability of the many Focomat 1C, Focomat IIC, and V35
enlargers out there in the world.  I would especially like to see a new 60mm
Focotar design for the IIC enlarger.  What chance is there of this?  I won't bet
on it! 

Ferrel Anderson
Davenport, IA USA