a pixel on an lcd creen will change color depending on the voltage aplied to it, but it doesnt actually produce light like a phosphorous cell in a crt. lcds are subrtactive, they take away from the light produced by the blacklight, where crts are additive they create light directly (all while blasting your face with an elevtron gun). an lcd display may be transparent if need be, but those require ambiant light to function. in the case of lcd projectors, they use the same kind of lighting used in film projectors its just instead of going through film, it goes through a fixed transparent lcd wich produces the same effect. they probibly also use the most power running a very high wattage lightbulb. as for screensavers, never use em, the bast way to save your screen is to turn it off when you are not using it.
