Originally Posted by curttard
Doesn't the gain apply to the dark elements of the image equally to the light, lightening the darks to the exact same degree it lightens the lights? If not, why not?
If one uses a Flat, Mono-colored surface, yes. But that is a very narrow view of only a specific aspect of gain.
If one has a surface that is sufficiently dark, yet contains elements that can collect and distribute just enough light to infuse the surrounding area with light, the end result is that the lighter elements retain a higher percentage of illumination than the darker areas correspondingly lose "black". The end result is a conservation of light, the retention of enough to in the least maintain a higher degree of Gain.
This should be very easy to grasp....it's a primary principle behind all the Mfg Ambient Light Screens, most all of which use either reflective particles or diffusive layers to collect and return light more on axis, and who use very dark substrates to also helpmaintain Black levels while doing so.
Despite what a few others might say, it's been done very effectively using metallic infused paint for quite a while now. Such is the reason that screen shots taken of such screens can show performance that simple Gray examples cannot unless the screen is very dark Gray, and inundated with excessive light...and that all too often winds up being counter-productive.
I have said many times that Gain in and of itself is not a valid answer for improving ambient light performance...even if it's centered around reducing reflections by directing light forward into center. And obviously that is accepted by those who must make Mfg Ambient Light Screens and charge an arm & leg for them as they all, everyone combine gain with a very dark surface.
Originally Posted by ahajr143
Gain has to do with the amount of light reflected by a screen compared to a white reference standard. Greater than 1.0 means the reflectivity of the screen is higher than the reference. A gain of less than 1.0 reflects less light than the reference standard. Black is the absence of light and white is the presence of all colors of light. When you have a gain of greater than 1.0 the amount of light reflected is greater for white and all colors but black, since it is the absence of light, has nothing to reflect. Therefore the difference in light between black and white is increased leading to the increase in contrast and the colors "popping".
While all the above in quote is all essentially true, the one obvious commission is that Digital PJs actually project Black as a "reduction" of light, unlike CRT PJs that project Black as a absence of light. Therefore, Contrast can be grossly affected if too much gain is present. That is why some PJ Mfg utilize a variable Iris, that can reduce light when a darker scene is in play. The best PJs do it somewhat differently, using improved light isolation within the Light Engine to help the image as it exits from the Pj start out as "Contrasty" as possible.