The most light-absorbent material?

July 30, 2009 10:22 AM

I need to stop a projection from showing up on a wall -- is there a particularly light-absorbent material that I could use?

At gigs around where I live, it's become reasonably commonplace to replace light shows with a pre-prepared projection shone directly onto the band and the wall behind them. I had the thought that it'd be really neat if there was some material that I could hang up behind the band that the projections wouldn't show up on -- so that the crazy projections showed up only on the musicians and their instruments, and everything got a little more surreal.

An AskMe search turned up a similarish question of asuh's about what kind of curtain material blocks out the most light, with the general answer being velvet blackout drapes. It's a slightly different ask, but would they perhaps work best in this situation, too?

Needless to say, if anyone has a different solution to the problem ( ~ that of how to have particularise what a projection shows up on ~ ), I'd love to hear it. Barring science-fictiony unnattainables like this, how do you think I should go about this?

posted by Rumpled to clothing, beauty, & fashion (9 comments total)

If not black velvet, then ultra-flat black paint.
posted by polyglot at 10:26 AM on July 30

Hang the projector such that it's pointing down at an angle to the stage. You can adjust the keystone of the image if you want non-distorted pictures on the band. The rest of the light will hit the stage instead of the backdrop - obviously the effect will be better if it's a raised stage.
posted by backseatpilot at 10:27 AM on July 30 [1 favorite has favorites]

A few points-

1: For the record, the unattainable you link to wouldn't work any better for visible light than black paint. The wavelengths of interest (see the data plot) are the mid-infrared and longer.

2. backseatpilot's idea is incredibly clever and likely to work quite well.

3. Another way to do this is get large polarized sheets which are cross-polarized with each other. That will absorb light quite effectively. The light from most (all?) projectors is polarized, so you can have some interesting effects with projecting onto a polarized surface. In fact, I have a friend who used to have a company where projection was important, and I had suggested a similar idea to reduce background light on a polarized surface by matching the polarization of the projector. Unfortunately, 2 of the 3 colors from the projector had one polarization, and the other color had orthogonal polarization, meaning you'd reflect some colors but not others, depending on the rotation of the sheet. I mention this because it might just be an interesting effect for what you're trying to do.

4. Flat black paint or black velvet would probably be sufficient and would certainly be A LOT easier.
posted by JMOZ at 10:41 AM on July 30

There's a venue that used to be in Salt Lake City (maybe it still is, but I don't live there anymore) where the back wall of the stage was a corner with mirrors on both walls. This trick worked there. So get two giant mirrors and angle them toward each other at a 90 degree angle behind the band.

The high angle thing suggested by backseatpilot will also work, and won't be a logistical and financial nightmare like my idea, though.
posted by The World Famous at 10:46 AM on July 30

Flocking. You can find rolls of it with a sticky backing so that it's easy to put up. Probably not as cheap as paint, but also not as expensive as a curtain.

I also like the idea of just pointing the projector differently, either towards the ground or the side so that the light ends up in the wings instead of the backdrop.
posted by kiltedtaco at 11:46 AM on July 30

How deep is the stage? Can you focus the projector near enough so that the images are sharp on the performers but blurry on the back wall? Probably would be good along with velvet/black paint.
posted by clorox at 1:12 PM on July 30

You also could project another light source onto the back wall to wash out the projections.
posted by Pangloss at 4:06 PM on July 30

You could shine two projections - one from either wing of the stage, so that they shine on both sides of the performers, but then just end up on the sides after that, rather than behind.
posted by The World Famous at 4:35 PM on July 30

Reading this question reminded me of Phoenix's "1901" music video.

I researched how they did it, but after looking at some of their "backstage" photos, it looks like it's more a matter of camera-play (faster shutter so that only the brightest light comes through) than actual light-absorbing materials.

If anything, it's a good case study of how cool the look will be if you can make it happen successfully.
posted by carpyful at 10:32 PM on July 30