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After all, a projector emits light, and darkness is simply the absence of light. You can’t “make” darkness, you can only remove light.

I understand all this… But when I watch a movie, the “black” that I’m seeing in a particular scene isn’t the absence of light, because it’s not actually “black.” It’s a very very dark shade of grey or brown or whatever. And that requires light. Even if there is some actual “black” (spots where no light is coming out of the projector), there will still be a gradient, and immediately after “no light,” you will have a light attempting to project a very dark shade. And that will need light from the projector to display.

Maybe there is a way to encode a video for projector that accounts for this, I don’t know.

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GreatAlbatross@feddit.uk ⁨1⁩ ⁨day⁩ ago
Maybe the best way to think about it is not dark, but the absence of more light. On a DMD projector, we use tiny micromirrors for each pixel which flash thousands of times per frame of video.
The flash/no-flash ratio decides how much light makes it out of the projector. This gives us thousands of light levels per colour channel, from near dark, to full light.
When the mirrors are not in position, the light output is very low. (1/1000th of the full output, on a projector with a static 1000:1 contrast ratio)

The screen is designed to reflect light well, which means in a non-perfect room, it will have a light floor of the reflected ambient light, plus whatever still makes it through the projector (as Cygnus mentioned, room treatment).

If you do treat a room well enough that the small amount of light that makes it through the projector at all-off is a problem, you can do things like fitting an ND filter to the lens (reducing the full light output, while also reducing the minimum). Or you can use the dynamic iris fitted to some projectors (which reduces the amount of light being put out based on the overall scene illumination, similar to the way LCD TVs lower the backlight level to “reach” contrast ratios of 100000:1).

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cygnus@lemmy.ca ⁨2⁩ ⁨days⁩ ago

But when I watch a movie, the “black” that I’m seeing in a particular scene isn’t the absence of light, because it’s not actually “black.” It’s a very very dark shade of grey or brown or whatever. And that requires light.

What you’re seeing are the deactivated TV pixels absorbing light. This doesn’t work with a projector screen because the screen is of course designed to be reflective, otherwise you wouldn’t see anything. Point a projector towards a piece of black velvet and you see… black velvet.

Even if there is some actual “black” (spots where no light is coming out of the projector), there will still be a gradient, and immediately after “no light,” you will have a light attempting to project a very dark shade.

This is the contrast I was referring to earlier. It’s basically the accuracy of the projector in defining a limit between the areas it’s lighting up. But if you do this in a room with the lights on and the windows open, the image will be completely washed out regardless of how high the projector’s contrast is.

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