I have a movie projector which is projecting an image on a brown wall. The projector allows me to adjust 6 values. Red brightness, Green brightness, Blue brightness. Red contrast, Green contrast, Blue contrast.

Is it possible to "cancel out" the color of the brown wall by adjusting the RGB values of the projector? By cancel out, I mean so that the end result of the projected image is equivalent, as if the wall was a more neutral gray or white.

If this is possible, is there a way to do it without an expensive colorimeter? Maybe with some image processing from a phone camera?

  • $\begingroup$ Wouldn't it depend on what colors the wall reflects? If it's painted with en.wikipedia.org/wiki/Vantablack you won't have much luck making it reflect white. $\endgroup$
    – endolith
    Jul 20, 2017 at 21:50
  • $\begingroup$ Ha hopefully not that intense. But a darker color should still work (like a gray). $\endgroup$ Jul 21, 2017 at 3:24
  • $\begingroup$ But you get the idea? If the wall is white, it reflects all colors, so illuminating it with only red will make it red. If the wall only reflects green, then it's not possible to make it red. The red will just be absorbed and it will stay black. In reality probably all walls reflect some of each color? But it depends. $\endgroup$
    – endolith
    Jul 21, 2017 at 3:36
  • $\begingroup$ If the wall reflects 'half' green, what would happen if you reduce the projector's green RGB value by half? $\endgroup$ Jul 21, 2017 at 3:42
  • $\begingroup$ It would be darker green? $\endgroup$
    – endolith
    Jul 21, 2017 at 4:46


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.