Archived posting to the Leica Users Group, 1997/12/10

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Subject: Re: [Leica] filters for M-lenses
From: "Henning J. Wulff" <>
Date: Wed, 10 Dec 1997 22:06:10 -0800

>I would like to buy UV-filters for my M 50/2 and M 28/2.8 lensens.
>I am still hesitating to buy the "Leica" filters. Maybe there is a less
>expensive alternative with equal quality or am I wrong?
>Who can give me some good advice on this subject?

This sort of question (and it's a very valid one) comes up regularly in any
photo discussion. There are a bunch of issues here.

If you think you need a UV filter (because you regularly go for your camera
in the middle of eating a pizza, and the camera is in a position where the
first thing you touch is the front element of the lens, or you're in a
dirty, spitting environment) then get a filter. I don't eat many pizzas
anymore, and I rarely need a UV filter. That largely sums up the arguments
for and against filters.

All filters degrade image quality. If you can see it or not is a separate

Most filters nowadays have plane surfaces. This was not always so. Beware.

A lot of filters even today do not have parallel surfaces. This is a big
problem and can cause major image degradation. With non-multicoated filters
that aren't too dense, you can check this yourself. Put the filter down on
a dark, flat surface and observe a point light source or other clear, sharp
edged light source that is reflected off the filter at about 45 degrees.
You will see the primary reflection from the top of the filter, and a
secondary, fainter reflection off the bottom surface. These will be offset.
Rotate the filter while observing these reflections. If the two reflections
move with respect to each other as you rotate the filter, the two surfaces
of the filter are not parallel to each other.  It's as simple as that.

If you have a filter that has non-parallel surfaces, it will wreak havoc on
the performance of highly corrected long focal length lenses. On a 50mm
lens you probably won't notice anything. On a super wide lens you will
notice performance drop off at the edges.

Polarizers have a whole slew of their own problems, and you will find it
difficult to get a polarizer for an apochromatically corrected lens of
200mm or more that does not degrade the image to an unacceptable degree.

At the moment I have probably over 400 filters from 22.5mm to 6", and I bet
that  95 percent are not good enough optically to put over certain critical
lenses such as a 47mm Super-Angulon XL or a 400mm apo lens.

The poor filters include all makes, and certainly Leica and B+W. On the
whole, though, Leica filters have been much better than average, and B+W
have also been good. The worst have been Harrison and Tiffen filters from
the 60's and 70's. The center filters that Zeiss made for the 15mm Hologon
camera and Leica mount lens is also not very good, having sharp cutoff at
the edges of the center grey part instead of the smooth transition it
should. All the Schneider Center Filters I have and have had (about 8) have
been better.

No company has a lock on good, or conversely, bad quality. You have to
check the filters yourself, and you have to check and test each one, if you
want to be sure!

A good quality, thin, plane and parallel surfaced multicoated filter set
correctly without stress in its mount will not usually degrade the image of
a 28 to 100mm lens. Beyond that get extra fussy. It's true that camera
shake and improper exposure will ruin many times as many pictures as a bad
filter, but if you are shooting with Leica glass, why handicap it?

   *            Henning J. Wulff
  /|\      Wulff Photography & Design
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