In article <33CD1480.1EAF@ctron.com>, dmarsh@ctron.com says...
>M. Noecker wrote:

>> I read that using these filters to protect the lenses wasn't really a good
>> idea because it meant two more layers of glass to shoot through. Does it
>> really make that much difference in the finished product? Any
>> preofessionals out there with the answers? I was really startled to read
>> this.

>While i'm not a professional, and really have no hard core evidence, i
>too have read/heard this from a number of sources (mostly people who
>have to be real critical with their images.) It certainly makes
>sense... if i had the option of shooting through my car window or not, i
>would prefer not too. Maybe a little extreme example, but get's the
>point across. Anyone else have any hard core results??
>BTW... i dont use the skylight filter now for this reason...And i havent
>had any problems ruining my lens.

I set up a 400mm f3.5 Nikkor, aimed across our lake at the opposite
hillside (this lens is excellent wide open, and the toughest test for
negative filter effect is placing it on a wide-aperture long lens...),
and shot it wide open with and without a Nikkor 122mm UV front filter,
and with an without the 39mm UV rear filter. Other than a slight focus
shift noted when the rear filter was removed, no difference could be
found in the images made with no filter, either filter, or both filters installed. I am a nut about sharpness, and I leave UV filters on all my
lenses that will fit them... (And, BTW, a UV saved the front element of
a favorite lens from the damage that the filter received when someone
grabbed for the lens. Also, when shooting near our many local waterfalls
[and fountains], the filters take the scrubbing often required to remove
spray marks. I see no reason not to use UV filters, and though they do absolutely nothing but protect the lens [the lens glass absorbs UV light],
that is enough for me...)
Hope This Helps
(David Ruether - http://www.fcinet.com/ruether )