Thread: ND fader filter on LCD screen - strange behaviour

I'm a photographer, and have bought an ND filter for my camera.
When i put the fader filter on my camera, i have the ability to turn on of the rings, which makes it a certain amount darker for each step - usually nothing happens, if you just spin the whole thing around. But today i noticed this strange thing. When i move the entire fade round in front of my laptop screen, it gets darker.

Can you guys give me an explanation? Here is a video i recorded of the penomenohm: ND fader filter - LCD screen behaviour - YouTube

Do you have a pair of polaroid glasses?

Nope. i do not

Well, an LCD screen uses polarizing filters in its structure. Your ND filter is also polarized evidently, so as you turn it, you gradually orient the polarising layers of your ND filter and LCD monitor until they are perpendicular to each other, blocking the light from coming through. If you had polaroid glasses, you would have been able to do the same with them. Polarizing filter (photography) - Wikipedia, the free encyclopedia

From that page: