Overhead video projector too bright - Teacher complains!

[Hacksawbob]

perhaps I could have been clearer, I am suggesting two different types of filter Neutral density filters (no colour effect) and circular polarising the latter MAY make some colour difference to the projected image, not significant to make it not worth trying if it gets a mardy teacher of a fellow techs back its got to be worth a go!

 

The effect in photography as I'm sure you're aware is achieved by reducing scattering of light, however this is due to reducing reflected light coming at the lens from quite large angles in preference to a desired direction of light (usually from the sun). In this case the lens would be used in reverse with a relatively short distance between light source and filter. It probably wont have the same contrast altering effect as it has in photography.