Cover reduce light?

[Trigger Man]

To my suprise I was over at Kwirkys one day picking up a coral and he had just gotten a light meter. We ended up testing the difference between light to water, light with glass cover to water, and light with glass with lots of salt creep and some other guck to water. We thought that the light penetrating the glass that had lots of salt creep and some guck on it woud have a huge difference, but in the end the light readings came in very similar. I was suprised as I used to clean my glass lids covering my tank every day or so, but now I typically just lift my glass at an angle every day so the condesation drips back into the tank and then clean the glass every couple of weeks.