Your comments caused me to go back and re-read Gary's filter notes in
much more detail than I ever have before. A few observations:
1. Only the 50/1.4 was tested at all apertures with a filter
2. The degradation decreases (slowly) with decreasing aperture
3. The degradation in the 50/1.4 results is gone by f/8.
4. All other filter tests are done only at full aperture
5. Even a filter that passed the vertical autocollimator test
(Oly 1A) caused slight degradation at full aperture on the 50/1.8
A few conclusions:
1. Poorly made filters have a significant deleterious effect
2. Even expensive filters may suffer from poor quality control
3. Even the perfectly made filter has some minor deleterious
effect when shooting wide open.
4. When using a filter shoot at middle or smaller apertures.
Chuck Norcutt
Winsor Crosby wrote:
> You could be right, but it seems to me an expensive lens plus filter
> is a very expensive mediocre lens. You might be better off to get an
> inexpensive lens and risk damage.
>
> Look here:
> http://members.aol.com/olympusom/lenstests/default.htm
>
> Put filter in your browser page search function and you will find 4
> or 5 instances of adding filters of varying quality to various lenses
> and how they degrade the resolution.
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