Message
Re: [colorvision_group] Re: Projector Calibration? Waste of time!
2006-07-06 by CDTobie@aol.com
In a message dated 7/6/06 4:50:18 AM, martin@... writes:
And guess what: after that time, the image was still yellow! Maybe my
eyes were a bit less sensitive to yellow, but the color still was
obviously yellow, not white. Must be because my eyes and my brain know
what yellow looks like, so they don't need a direct comparison with a
different color to tell that it is not white. That's pretty logical,
because the brain can learn and remember. Otherwise you'd always need
a dog standing next to a cat to tell which one is the dog!
Dogs and cats are not white sources. Neither is a projected yellow image, if the lightest elements in it are white. Its when a given mix of red, green, and blue is used to define white, the brightest light in a space, that this tint becomes the whitepoint. There is a famous demonstration where a "white" circle is projected on screen. The audience agrees that it is white. Then a brighter circle is projected inside it, making the former "white" gray. Then a third, even brighter spot is projected inside the second one, and that is now light gray, with the first "white" now being darker gray. You could then change to a blue range, and it would look blue for a bit, but then, later, if you changed back to the first set of "whites" they would look yellow, as your eye had adapted to the blue series. As I noted earlier, its not my intent to argue our way through basic color theory: get a text on the subject, and read it for yourself.
C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com