[Leica] To filter or not? [Long]

["delia" <louzan@worldnet.att.net>]

Bryan,

The first thing I do as soon as I buy a new lens is to put on a UV filter
(Leica doesn't recommend the use of Skylight filters since they change the
color transmission), and I never clean the front or rear lens elements. 
Why? 
Some time ago I realized that some of my slides, taken with those lenses
that I cleaned more often, didn't have as much contrast as others.  
I mentioned this to a friend, and he said he had reached the same
conclusion years ago.  Never clean a lens!!!
Today's MC and glass are harder than they used to be -- but most lens
cleaners are solvents, and over the period of a few years, you are going to
remove some coating or even scratch the lens.  All it takes is some cheap
lens cleaning paper.
I do, however, clean my Glass filters with a solution of 80% ether and 20%
ethanol (grain alcohol).  For my plastic and resin filters, I dilute a drop
of hand soap (that doesn't have moisturizer) in 1/2 gallon of destiled
water.  After blowing the dust off, I apply it to the filter with a piece
from an old cotton T-shirt that has been washed time and again.
As for used lenses, I do buy them (I'm talking old here, not last month's
demo) but I just don't expect them to perform as well as when they were
new.  With this in mind I've been pretty happy.
I'm sure I'm going to get a lot of fire on this one, but those skeptics can
run this simple test: buy a quality filter ex. B + W and clean it
occasionally with a handkerchief for a year.  You will see how the glass
becomes etched.

Regards,
Robert