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Path: utzoo!linus!philabs!sdcsvax!sdcrdcf!brad
From: brad@sdcrdcf.UUCP
Newsgroups: net.rec.photo
Subject: Re: Filters
Message-ID: <330@sdcrdcf.UUCP>
Date: Thu, 16-Jun-83 09:21:58 EDT
Article-I.D.: sdcrdcf.330
Posted: Thu Jun 16 09:21:58 1983
Date-Received: Sun, 19-Jun-83 04:15:40 EDT
References: <359@ihuxw.UUCP>
Reply-To: brad@sdcrdcf.UUCP (Brad Spear)
Organization: System Development Corporation--a Burroughs Company
Lines: 23

In reference to the question about Skylight 1A and UV filters:

Both the Skylight 1A and UV filter some blue-violet-ultraviolet. The UV is
specifically used for the Ultra-Violet, while the 1A also 'warms' the scene
somewhat. If you look closely at each, the 1A is 'pink', while the UV is
visibly clear. (It wouldn't be if you could see UV)

The reason for filtering UV is because the film in your camera is not
sensative to the same range as your eye, it can 'see' the UV, which will
make your photographs come out bluer than normal. This is normally not a
problem, but can be, especially at midday and at high altitudes. In these
cases, sunlight is considered 'cool', because it consists of a high
percentage of 'blue' light, as opposed to morning, evening or low altitudes
where the light has less blue and more 'red', thus being 'warmer'.

They are both also used as lens protectors, since they pass what you see
relatively unchanged (except 1A is slightly redder) and are much cheaper
than a lens. I don't want the warming of a 1A usually, so all my lenses are
fronted with a UV. The distortion of a good quality filter is usually
negligible.

					Brad Spear
					sdcrdcf!brad