[Leica] UV/IR filters

[lrzeitlin at gmail.com (Lawrence Zeitlin)]

Traditional wisdom is that the UV or IR filter creates another layer of
glass in front of the lens,  increasing the number of reflective surfaces
and possibly degrading the image. I've never actually seen this demonstrated
with a high quality glass filter nor have I ever seen a definitive test of
this assertion. Erwin Puts, where are you?

However I generally used UV filters for another purpose. In my industrial
consulting work I often took pictures in dusty factory and field
environments. Most of my travels took me to dry, sandy or very wet places. I
felt much better wiping the grit or salt spray off of a $10 filter than off
of a $1000 soft coated front lens element. If I cleaned too vigorously or if
a metal chip flew off a grinding machine machine and scratched the filter, I
could replace it without the agony of fudging an expense report. Admittedly
I never had the experience of jamming a tripod tip directly into a lens and
watching the filter break into a million jagged pieces. But then I suspect
that few of us have. I did have one experience of swinging a shoulder
strapped camera into the sharp corner of a metal shop table. The corner hit
in the center of the lens but the filter merely cracked. The metal rim held
it together. I simply removed the broken filter and worked the rest of the
day with an unprotected lens, holding the camera more carefully.
Larry Z