Archived posting to the Leica Users Group, 2000/01/24

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Subject: [Leica] Systems theory
From: Mike Johnston <>
Date: Mon, 24 Jan 2000 16:21:42 +0000

>>>You mentioned yourself: "...assuming you believe in systems theory".
That's the key, it's a theory.  I need to understand, when reading lens
tests by those who employ MTF measurements (or any other test or
evaluation, for that matter), what the assumptions are that those tests
rest upon (such as systems theory and well focussed images) to
understand what they are (and are not) testing.  I then employ that
knowledge, along with the knowledge of what *I* believe, understand and
have experienced, to draw conclusions about suitability<<<

That's the crux of it. There is a seldom-acknowledged but very severe
disjunct between what we call "optical quality" and properties that help
make a photograph artistic or expressive. Everyone is aware of the
"Diana" camera fad in the '70s whereby people used a cheap toy camera
with a single-element plastic lens to create art photographs. Like 'em
or hate 'em, you have to acknowledge that the results fit the makers'
expressive intentions better than a "better" lens.

Sally Mann uses a fine Schneider 300mm f/5.6 lens, but she uses it
almost always wide open, where it vignettes fiercely and smears more and
more as it gets more towards the corners. She likes the "old fashioned"
or "dreamy" look of the lens. Again, here's an example where technical
performance as it's commonly understood would be a detriment, not an

Regardless of what you think personally, there is no correllation
between conventional "optical quality" and successful expressive
photography; it's easier to find examples of negative correllation. So
we have to realize that the basic predicates of most "lens testing" may
in fact be useless to certain individuals vis-a-vis their needs.

Incidentally, "bokeh" qualities can be measured; it just isn't done in
conventional lens tests.

I received two British reviews of the Hexar RF in the mail today from Ed
B.--many thanks, Ed.

- --Mike