[Leica] Testing lenses wide open

[John_McLeod@designlink.com]

Dear LUGgers:

I just read Ted's post about testing his lenses wide open.  I have a question
for you Ted and others in this regard.

Since discovering, several years ago, that my prized 80/1.4 R lens was
extremely soft wide open, I have resolved to test every lens that I might
purchase at its widest aperture.  I have become obsessive about this almost to
the point of  absurdity (for all non-Leica people, I have reached and pushed
past the point of absurdity.  Ask my wife).  I say this because, unlike Ted, I
usually shoot somewhere in the middle.  With Ted's encouragement, I may become
seek to be transformed into ... "Noctilux Man".

Since discovering the problem with the 80/1.4 (returned to Leica along with
$500 in exchange for a new 100 APO-macro), I have probably tested 10 lenses
wide open -- some Leica, some Nikon, some Canon.  When I say tested, I mean
something between what Ted and Erwin would do -- closer to you though Ted :)  
That is, on a tripod, with 100 ISO chrome film at 1.4, 2.0, 2.8, 4.0, etc.,
then with a 15x Peak loupe and lots of eye strain (remember my light box
question?).

While I have been careful about testing, I will admit that the following is
anything but scientific, and due, I am sure, only to chance.  It seems that
several lenses that I have tested wide open excel at resolving fine detail but
lack contrast.  Take the following two Nikon 50/1.4's for example.  Lens A is
tack sharp wide open.  Light fall-off is negligible.  Contrast and overall
saturation ("punch and pop") are low relative to lens B (or to lens A at
mid-apertures).  Lens B is not quite as sharp wide open, exhibits more light
fall off, but produces more contrasty, saturated slides.

My questions are:

Is it just chance or is there some predictable/logical relationship between
resolution, light fall-off, and contrast (at wide apertures)?  In other words,
do the highest resolution lenses with minimal fall-off tend to be less
contrasty, or can I just chalk this up to luck?  Second, all other things being
equal, which is generally preferable for wide open shooting -- a lens that has
great contrast wide open, but some fall-off and pretty good sharpness, or a
lens that is extremely sharp with little fall-off, but lower contrast?

How's that for a long-winded question?  Thanks in advance.

John McLeod