Quote Originally Posted by Pere Casals View Post
I also agree that UV contribution to exposure would be low at sea level.

In this (wiki) graph we see in red the sunlight spectrum at sea level, so it's easy to figure what exposutre contribution eliminated by an UV filter would be modest.

The yellow graph shows the spectrum outside of the atmosphere, so in high mountain conditions we would have an intermediate situation.

He is taking a picture of the sky, not the sun.