Has anyone painted wall 18% gray?

Discussion in 'Archived Threads 2001-2004' started by Marc Rochkind, Jan 14, 2002.

  1. Marc Rochkind

    Marc Rochkind Second Unit

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    I read somewhere that the best light for a non-front-projector TV was a 6500K light shining on the wall behind the TV. The wall should be painted 18% gray (Zone V, for you Ansel Adams fans).

    I'm curious... has anyone actually done this?

    Just for fun, I had my local paint dealer match an 18% gray card. I have the Benjamin Moore recipe if anyone wants it.
     
  2. Ron Shaw

    Ron Shaw Stunt Coordinator

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    When I turn off the lights, even my white walls look black!
     
  3. Ergin Guney

    Ergin Guney Agent

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    Marc,

    I don't know where the "18% gray" requirement comes from, but something about it doesn't sound right to me. What matters about the wall behind the display is what shade and brightness it appears to you. The NTSC spec similarly states that the surface behind the display should appear as an evenly lit surface of brightness equivalent to the display's 10 IRE, with an 6500K color temperature.

    What I'm trying to get at is that, what the wall "appears as" is function of not just the shade of its paint, but of the combination of the shade of its paint and the light source with which you are illuminating it. Like Ron already pointed out succinctly, you can have white walls and have them appear as pure black by not illuminating them at all. Or you can have a wall that is painted a 50% gray or darker, but then illuminate it with a light so bright that it ends up appearing brighter than a 100 IRE white shown by the display in front of it.

    I think it's moot to focus so closely on the shade of the paint alone without talking about the power of the light source with which you are illuminating it, and from what distance, etc. So I don't think there can be any single "correct" shade of gray to put forward as a requirement for the wall behind the display, when the second half of the equation depends on the power of the light source and is not fixed. Technically, you can get the right 10 IRE gray illumination with any shade of gray paint on the wall as long as you can vary the power of the light source illuminating it as widely as you want (provided that both the gray of the wall is of neutral chroma and the light source is at 6500K).
     
  4. TimG

    TimG Second Unit

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    I think the 18% grey is mostly for front projection, as it is neutral and will not cause the picture to be "colored" by say a green, wall. My room is a lighter green and it does affect the color balance slightly, but my wife wouldn't let me go with grey or black. I don't think it is necessary when you are using a direct view or rptv. Just my .02

    TimG
     
  5. Marc Rochkind

    Marc Rochkind Second Unit

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