Photographing video screens ... a question about how they work?

[jaredangle]

The other evening while shooting a gallery opening of video art I ran into a problem that I've sort of had before but not to this extent. Most of what I shoot at these things is in on monitors and projection screens and while they can be very hard to meter because they're constantly changing I take plenty of shots to cover my arse so to speak! 😀

I struck a screen the other night that sent my poor D700 into a fit ... every time I took a shot of it and reviewed the image it would be a different colour ... bright orange, blue, green and then occasionaly (very seldomly in fact) completely normal. I never managed to get a successful image of the damned thing the entire night and in fact I'm going back to the exhibition later today to have another go at it. I was talking to the tech who sets these things up and he concluded that maybe some of these digital projectors pulse alternately between the primary colours at a rate that the human eye doesn't notice but the camera singles out these phases at faster exposures ... but why just this screen?

Does anyone have a technical explanation of what may be happening here?

for my college newspaper, one assignment I had to photograph was a multimedia display of character/model created by a graphic design student. The display consisted of four posters representing the concept art, polygon mapping, texturing, and animation of the character. In the middle of the posters was a clay sculpture of the 3D character, and at the far end of the exhibit was the full range of motion of the character displayed on a looping video on a large plasma tv.

For the photo of the TV, I photographed it multiple times at a medium shutter speed (I think 1/60 with an 85mm on my D700) which was exposing for the near-black color of the TV. The 1/60th shutter speed was long enough to cover the sync rate of the television (probably between 60-100hz)

But this long of a shutter speed also overexposed the image of the character by about two stops. I returned the character to his proper brightness in relation to how he actually looked compared to the monitor by making a selection of just the character (background was black) and duplicating the layer twice, making three layers (background, character duplicates 1 and 2) and setting the two duplicate layers to a blending mode, I think darken or burn or something like that in photoshop, which returned it to its proper brightness, contrast, and saturation.

 

[_larky]

To the OP, I know you will get no say maybe, but if they ask for your advice on panels for future exhibits, ask them to use Samsung 550EX and 460EX. Ultra thin, great panel, LED based commercial gear and you'll photograph it easy 🙂

Viewing angles are incredible.