Here is my idea of estimating contrast ratio, assuming the worst possible case: whole screen displays white, with only a little black area. So, as we expect, there will be lots of reflected light in the room (there is white ceiling, shiny floor, bright walls, and so on). There is an example in the picture below. These areas from the left are as follows: a perfectly black, wide border, painted around my screen, "projected black", and projected white. In fact I cheated about this middle "projected black area", the projector was slightly shifted right, so this middle grey stripe is just an edge of my white screen, but outside the projection. So the real "black" from the projector would be even worse. The picture was converted to grayscale, perharps camera sensitivity is not linear, but for the eye it looks about like you see here. There isn't any black, it's a moderately light gray, pixel values are like 32-35, while black on the left are like 2-3, and white 120-170. What would be the contrast ratio there, assuming roughly linear camera response? About 5:1, am I right?
Of course in reality we would never watch a white screen, it will always be overally dimmer, so less light reflected from the room, and darker "black". But never really dark. And this case would look the same with a high-end, high contrast projector. High contrast would never make this gray area black, as it's lit by the reflected light. The higher the lumen output, the more reflected light, and perharps this is a linear function.
The oposite experiment, for best case, was done by renan in the thread "real lumens output measurements", and I believe his stated value of about 100:1. It will always be much lower then the original contrast ratio of the LCD.
Regards
Of course in reality we would never watch a white screen, it will always be overally dimmer, so less light reflected from the room, and darker "black". But never really dark. And this case would look the same with a high-end, high contrast projector. High contrast would never make this gray area black, as it's lit by the reflected light. The higher the lumen output, the more reflected light, and perharps this is a linear function.
The oposite experiment, for best case, was done by renan in the thread "real lumens output measurements", and I believe his stated value of about 100:1. It will always be much lower then the original contrast ratio of the LCD.
Regards
