[Leica] Image quality

[Erwin Puts <imxputs@knoware.nl>]

Some Leica lenses are well-known for their uncanny ability to record 
extremely fine details in the object on the film. The big question 
many Leica users will be asking is this: can we get that quality on 
paper? We all know that every step in the reproduction process will 
degrade the image quality somewhat. Some writers/observers will even 
claim that this degradation is quite severe and will make the 
difference between a picture made with a Leica lens and a Pentax lens 
(as example) marginal if not hypothetical.
So I went into the darkroom to check if I can transfer the potential 
image quality of a Leica lens  to paper without a significant loss.
I used the Summicron 2/50mm (latest generation) and a Ilford 100Delta 
in Rodinal, compared to a Kodak TMax100 in D76. Aim of this test was 
not to verify if the Pentax lens would be as good as the Leica lens 
when transferred to paper, but to see if the image quality of the 
Leica lens could be preserved on paper when using different 
film/developer combinations. The theory behind the choice is the fine 
grain versus acutance type of development for preserving image 
sharpness.
To get some tangible results I used a resolution chart. The Summicron 
50mm will resolve 40lp/mm with good contrast as the MTF curves will 
tell you. Now 40lp/mm is quite a bit: it means that 80 lines per mm 
will be detectible with great clarity on the negative, each line 
having a width of 12.5 microns (thousands of a mm). The question is 
now: can I get the same definition of fine detail that is delivered 
by the lens on paper when I use a negative, an enlarger and a print.
At enlargements of about 10 times I could not detect the same 
definition. It was always lower. Now when enlarging to 16 times from 
the full negative I clearly saw the fine details that are equivalent 
to that resolution of 40lp/mm. . If I had used even finer grained 
film with a bigger enlargement the film/enlarger/paper combination 
would get me to about 80lp/mm, which is about the maximum any 
well-corrected lens can deliver in practice.
I used the Focotar 2.8/40. At 2.8 (just as an aside) the resolution 
was  below my expectations.Stopped down to 5.6 the world was OK.
So this test indicates that the high quality of a Leica lens can be 
put on paper and be visible by any observer with an unaided  eye. The 
100Delta was ahead of the TMax100 in this discipline. By implication: 
if a Pentax lens were as good as a Leica lens, it would show. If not, 
it would be visible too.
Conclusion: with suitable material and technique Leica lenses can be 
made to deliver their image potential on paper.  But a negative needs 
to be enlarged to at least 12 times to show the decisive advantage. 
Or you need a very critical eye.


Erwin