On Wed, 30 Oct 2002 17:35:01 -0800 (PST), bigrocketman3@webtv.net (Steve McDonald) wrote:

[you have an unfortunate habit of disconnecting your comments from the thread involved, which removes
all previous arguements/information - for those who missed
the post SMcD is referring to, I add it below:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"On Wed, 30 Oct 2002 01:23:34 -0800 (PST), bigrocketman3@webtv.net (Steve McDonald) wrote:

> Sceptics about the optical effects and value of using Ultra-Violet/
>Haze filters might check out this website presented by Nikon. The first
>link is a direct one to the section about UV/Haze filters. There are a
>number of sample pictures made without filters and then some made with
>many of the popular brands. Note that there is an unequivocal reference
>to the effect UV light has on both film and CCD photography. As I have
>seen in my own video recordings, there is a portion of the UV light
>spectrum that is above the frequency we can see directly, but is
>detected by CCDs and which alters video images. The aspects of haze
>reduction by these filters is also discussed.
>
> This Nikon website, that is featured by MTU on their pages, also
>contains good information about many other subjects related to film and
>video photography.
>
>http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/filter/filter-UV.html
>
>http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/950/index.html
>
>Steve McDonald

Well, from the first site you gave, I had trouble detecting
any material differences at all in the first UV/no-UV images
(viewing the enlarged images on two different monitors, with
the different-colored edges removed) other than exposure in this first pair and a slight blue predominance in
the "with
UV filter" example (which is odd, since the UV filter is
purported to reduce excess blue from UV-sensitive film - and
these examples were from film images, with film being more
sensitive to UV effects than CCDs...). In the set of images
with no-filter, followed by examples with six brands of UV
filters, the images again show that there really are no
significant differences. With the various skylight filter
brands, there are slight color casts, as expected - these
all have color, and it varies in strength and color among
the various brands. BTW, the verbal descriptions of the effects of the UV filters are not supported by the
images
themselves - though some UV filters do have a slight yellow
color, affecting the results VERY slightly... Your second
example merely refers back to the first, which does not add
support. I think the Nikon page simply supports what I have
been saying with the examples, if not with the erroneous
text - and, one must always question the mythologies that
are present in photography (though there numbers are tiny
compared with those that abound in audio...;-). Again,
with multi-element glass lenses, very little additional UV that could be imaged will be absorbed using a UV
filter,
and unless the color in the filter is significant, and
unless the WB is locked, there will be no significant
effect on the image when a UV filter is added - and this
is especially true for video since CCDs are less sensitive
to UV than is film... If you can present honest side-by-side
comparisons that can show a significant difference from
adding a *colorless* UV filter in video, I'm interested in
seeing them - but this site fails to do this... (I may
do this myself, to show that there is no significant
advantage to using UV filters except for lens protection).
David Ruether"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~]

> Yes, I can imagine how objective your own UV-filter picture
>presentation would be, since you have already selected your position on
>the subject and you're sticking to it.

All the evidence presented (by both of us, as it
turns out...;-) supports the fact that UV filters
will not appreciably affect a video image under normal
circumstances - and anything I put up is therefore
likely to show (again) the same thing. Rather than my
bothering to repeat the obvious, I have invited you to
prove your own point with comparison images on a web
page of your own (a more useful thing), but you have
not done this. The web page you presented in support
of your belief actually supports mine in its comparison
images, if not in its verbal claims...;-)

> In fact, I can see striking differences in the brightness and also
>the resolution in the examples on the Nikon page.

A discussion of human perceptions may be in order here,
but it is maybe too complex for now. My experiences in
audio, though, taught me a lot about people's abilities
to hear/see differences when they actually do not
exist...;-) Also, perhaps you should check your monitor
for evenness of illumination, color, and focus across
the screen? These do vary in most monitors...

>As explained on this
>website, the shorter wavelengths of UV light are reflected by dust or
>smoke particles to a greater degree than the longer wavelengths of the
>visible blue/green/red parts of the spectrum and this reduces
>resolution. By filtering out these UV reflections, much of the optical
>effect of the air pollution is removed.

Possible, but unlikely, if the system passed UV
(see old photos shot with UV-sensitive film and
simple lenses that did not block imaging UV - the
image is still sharp, with a "halo" of out of focus
imaged UV); impossible, if without the UV filter in
place, image-forming UV has already been removed,
as it has been in most video systems... If I give
you a red monochrome image, I cannot then tell
you that adding a deep red filter will further
reduce the green/blue content, since no green/blue
is present to begin with... If no UV of interest
is already present in the video image due to the
filtering effects of the glass in the lens and the
low UV sensitivity of the CCDs commonly used, adding
further UV filtration will do very little (certainly
less than the vagaries of auto exposure and auto
white balance will introduce in terms of visible
effects...).

> These pictures are there for everyone to see and judge for
>themselves, so they won't need to be influenced by what you or I have to
>say. It's nice to have visual evidence to support one's opinion, making
>further comment unnecessary.
>
>Steve McDonald

I agree...;-)
And, they are at:
http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/filter/filter-UV.html,
for those interested in seeing what obvious effects
adding six different brands of UV filters have
compared with using no filter (remember that some
UV filters have a slight density and a slight
yellow color - and that all "skylight" filters
are slightly pink/salmon in color...).