I was just wondering what the difference is between a multi-coated filter and a non-multicoated, and whether or not I should have them on my lenses (if I don't already). I have a Tiffen UV filter and a Sunpak UV filter...is this something I should be thinking about? Also, what's the difference between just a standard UV and a UV/Sky 1A?
Yes, you lose 1/3 to 2/3 stops of light with a non coated filter. You also increase the chances of stuff like flare, etc, and might end up with reduced contrast (though my main reason for using multicoated stuff is to prevent the loss of light).
The difference is as you've put it.. one is a UV, and one is a UV cum Skylight.
Not sure what you mean by basic; however, you can purchase UV filters in non-multicoated, multicoated, super multicoated, etc. In fact, when I purchased a couple thin ring filters for a wide angle lens last year, I found that one manufacturer (Tiffen) did not (at that time) offer multicoating for their thin filters. Therefore, I went to Hoya that offers an HMC multicoated filter that has the coating applied to both sides. I highly recommend not purchasing any filter, unless it is multicoated. It’s personal opinion; however, why spend a fortune on lenses, only to add a cheap filter to the front, and cut the light transmission due to non-multicoating.