Double the Power, Double the Contrast

Let’s examine the Race to Black theory a bit more starting with Table B, Black vs Contrast. This chart shows what happens when the black level is reduced while a white level remains constant similar to what happens with an optical projection screen. That technology has the ability to reduce ambient light at a different factor than projection light; effectively removing only ambient light, and lowering the black level, while leaving the projection light. In Table B the projection light level used is 400 nits at all times. ONLY the black level changes. The black level starts out at 50 then decreases to 1 by increments of 1. So, its change is 50/1 = 50; or stated another way, it is just 1/50 times less light than where the black level started. As it does this, the contrast changes as well. It starts at a value of 0.16 but then increases to 400. In total, the contrast change is 400/0.16 = 2500. So, the contrast went up 2500 times when the black level only changed by a factor of 50 times. What this shows is that a change in black level for an image is not proportional to the change contrast.

A change in Table A can also be seen but let’s explore this idea further to see how this breaks down. This chart shows the contrast level change as white is increased from 50 to 1000 nits, in increments of 5 nits. So, 1000/50 = 20 times higher at the highest point than the lowest. The black level stays constant at 50. Through this, the contrast increases from a level of 1 up to 20. So, the contrast change by adding white is 20/1 = 20; the same as the light increase. This shows that the increase in white and contrast is proportional when the black level remains the same. In effect, if a system uses double the power, then you get double the contrast. This is similar to what is done with traditional screens. The ambient light cannot be removed so all you can do is add more projection power.

When combined, these two tables illustrate that the key to success is a race to zero and not a race to more power. In an industry where designers are running with their hair on fire to add more and more power to overcome a room’s brightness, that’s a bold and confrontational statement. Yet, the reality is that at the end of the day the numbers speak for themselves. So, if you are a designer, stop, turn around and go the opposite direction. Get as black as possible and then work on the power level to get a proper white point. Once that is in place, you can indeed use projection in areas that you could not use before. Stay tuned for our next blog post regarding The Race to Black.

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