A note of caution when shooting through glass windows-
Last year I proved to myself there is a time not to use these clear filters, like the UV
or 1A Skylight. I was shooting through a glass observation window and picked up reflections of airframe highlights (silver US Airways vertical stabilizer leading edge-very bright!) just slightly displaced from the actual image. I went back a month or so later and shot similar aircraft under nearly identical light conditions without the UV
/1A filter and that particular problem was gone. I believe the highlights were being bounced off my objective lens onto the back of the filter and then back through the lens to the film. I should have noticed this when taking the first shots, but there was this little kid who kept trying to step into my camera case. Later he thought my sandwich was his........Considering he was someone else's child, it was pretty distracting.
(I'm getting better at these excuses):D