Re: M6 problem survey; 100/4 Elmar

["Patrick G. Sobalvarro" <pgs@sobalvarro.org>]

At 05:36 PM 9/6/97 -0400, you wrote:
>I never wanted to discredit you, neither personally nor in front of the
>group. 
>
>I've always appreciated your ideas, informations, comments and support, and
>I'm really sorry, that I stepped on your toes.

I think you're great, too, Alf.  But with respect to your critique of my
message giving the confidence intervals people had requested for Fernando's
numbers, I simply can't understand what you're doing.  Nothing that you've
said seems to me to make very much sense in the context of the problem
we're examining, and so I can only conjecture as to your purpose in
bringing up a list of techniques whose relevance to this particular problem
is at best questionable.  For example, in your latest message, you say that
a Poisson distribution should be used because "a broken M6 belongs to the
group of 'rare events'"; but this would simply be another approximation to
the binomial (and perhaps not such a good one, as n is relatively small and
p is relatively large here).  Your use of the word "event" makes me wonder
if instead you're talking about modeling the failures of M6's as an arrival
process, but we don't didn't get any time-frequency data in Fernando's
numbers, so this would be impossible without more data, and no one had
requested anything but confidence intervals anyway.

Anyway, perhaps we should concentrate on the things we agree on.  I agree
with you that it is bad for Leica to sell broken cameras.  I agree that it
is bad for them to take such a long time to repair broken things -- Leica
USA kept my slide projector for many months once, and I stopped using them
after that.  I agree that Fernando's survey data are interesting to
discuss.  I agree that Microsoft's software is often buggy.

- --------

Moving on to topics that may be of interest to more LUG members, I recently
bought a 100/4 Elmar for bellows.  I had previously done my macro work with
a 135 Elmarit-R and my 50/2 Summicron-R mounted on the bellows; but this
arrangement, while producing high-quality results, was pretty inflexible,
because I couldn't focus very far even with the 135.  I bought the 100/4
because it allows infinity focus on the Bellows-R.

I've gotten back some results now.  I tried the lens at a variety of
apertures and subject distances on E100S slide film.  I must say that,
while this lens is nice and sharp and contrasty in macro work, my
photographs of subjects at distances of several meters seem to be less
sharp.  This isn't actually all that important to me personally because I
bought the lens for macro work and the bellows arrangement is too unwieldy
to use for anything but macro.  However, given that this very lens is sold
in a focusing mount, I'm surprised at the lackluster performance.  Perhaps
it was operator error.  Has anyone else on the list used one of these
lenses (perhaps in the focusing mount) for non-macro photography?  How does
it perform?

- -Patrick