[Leica] Performers and flare

["Erwin Puts" <imxputs@knoware.nl>]

It was noted: "Once you get past Erwin's bench tests, is there really a
"bad" version of
the Summicron 35?...I've owned various versions over the years - I assume,
as I've purchased them all used at widely different period of my life - and
they've all be terrific performers."

If this really is what the poster assumes, I can only add: if your
definition of "terrific performers" is modest enough, he is absolutely
right. Most Leica photographers I know however see very discernable
differences. The performance you can extract from a lens is tightly coupled
to technical expertise and the level of your demands and your type of
picture taking. Without this background info any statement about good
performance is void.
The flare issue. Flare is defined as unwanted stray light, that will be
uniformly distributed over the whole image area. If we have a scene from
black to white, we will have a range of figures that indicate relative
contrast, we have a rnage of 100 to 0.25 lux, indicating light and dark
areas, which is a contrast of 400:1. Add a uniform flare level of 0.25 lux
and we now have 100.25 and 0.5, giving a contrast of 200:1. The effect on
the dark areas is big and on the lighter areas to be neglected. This example
shows two things: flare does simply give greater negative density in the
thin parts of the negative (the black areas), and will give a dark grey
instead of a black, suggesting detail, which is not there.
The old story that you can use a low contrast and/or flare prone lens to
compensate for high contrast in the scene is not correct. The highlights are
not affected and the dark areas just become muddy.
The best proposal: buy a high contrast lens, use a 100ISO BW film that gives
good toe density and expose and develop to get the maximum contrast your
print paper can handle.


Erwin