>> Since UV filters don't effect visible light,
>> they don't affect flare caused by a visible
>> light source in the frame.
> Any filter, UV, sky, or otherwise introduces
> two air-to-glass surfaces, either of which can
> create or amplify flare.
Pardon my sloppy speech. :O)
I meant was that it wouldn't REDUCE the flare caused by
visible light. An uncoated UV filter would ,of course,
contribute to visible light flare.
The intent of the message was to explain that while a
UV filter won't reduce flare in a single-coated lens
to the level that multi-coated lenses do, it will reduce
it to a noticeable degree.
Since my attempts at brevity seem to go awry in here,
there follows a second attempt:
Step 1:
Given:
1. The percentage of light that gets reflected rather
than transmitted increases as the wavelength of the
light decreases.
2. UV light has a shorter wavelength than visual light.
We can conclude:
Theorem 1.1 -- UV light flares badly.
Step 2:
Given:
1. UV light flares badly (Theorem 1.1)
2. For general photographic purposes UV light provides
little or no useful information in the final image.
We can conclude:
Theorem 1.2 -- Preventing UV from entering the lens is
a good way to reduce flare.
Step 3:
Given:
1. A UV filter does not significantly attenuate
visible light.
2. Visible light can reflect off of glass elements.
3. Coated elements transmit a higher percentage of
incident light than uncoated elements.
3. Multi-coated elements transmit a higher percentage
of incident light that single-coated elements
We can conclude:
Theorem 1.3 -- A UV filter will not reduce flare from
visible light, because visible light
will
still be reflected
by the internal elements.
Corollary 1.3.a -- An uncoated filter will increase flare
from visible
light, because it provides
an additional reflecting surface.
And in conclusion:
Don's Postulate: You can eliminate all flare from a lens by
simply removing the lens elements.
OK?
-Don
