[frank]

I don't think so. The main purpose is to limit the amount of direct sunlight entering through the lens. A telephoto lens has a bigger physical aperture size than a wide-angle lens. So at the same F-stop, you'll let more light enter the system with the telephoto lens - which is the main worry here.

I don't think so. What matters here is the solid angle of the lens to the sensor, not the diameter size of the lens element. At the same F-stop a tele lens has the same solid angle as a wide lens to a point on the sensor. But for a tele lens the light ray will hit the sensor more likely with a straight angle.