How does projectors project black colour?

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How does projectors project black colour?

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They don’t. It just depends on the contrast of the brightness of the other colors and the light in the room. If you shine a bright light where you’re projecting you’ll wash out the image.

They don’t. Ideally the black areas are where no light is emitted.

This means that black on a projected image can only be as black as whatever you’re projecting it on. So if the room isn’t completely dark, you can’t get good blacks. An extra snag is that of course a projector is a source of light, and light bounces around the room. Some of that is going to hit the areas that were supposed to be black.

They don’t, they just don’t project ANY light for black. Well they do unintentionally a little bit, because projectors suck… 5 figures or go home… Anyway ALL areas on the screen are reflecting just as much ambient light as with the projector off or on, everywhere, irregardless of what the projector is “throwing” at the screen or not. It’s just that how your eyes work, the significant additional light cast by the projector onto the screen and thus back toward your eyes for “bright” areas of the cause the ambient light reflecting only areas of the screen to now look relatively dark. Assuming it’s a decent projector and it’s projected image is taking up the ideal field of your view (how far you are vs. how wide the projected image is, I don’t remember the ratio) and the projector is actually putting out some decent lumens (expensive) your eyes iris will react to all that additional light and narrow down, now there’s actually less light from the “not light” areas entering your eyes, even though if you were to use a telescope or something to peek at a small “not light” area on the screen, it’d look exactly like it did before the projector was even turned on, assuming ambient lighting hasn’t changed.

This is why movie theaters are darkened.
This is why replacing your TV with a projector is one of those ideas that seem great, for about 5 minutes.

There is screen gain…
And ambient light rejecting screens…

And there are no miracles. Without a dedicated light controlled room, a room in which the flooring, ceiling, walls and even furniture have been chosen to reflect as little light BACK at the screen as possible and pollute that all important contrast ratio, projectors suck.

Actually this is how ANY TYPE of projector (doesn’t) project black. Slide film, movie film, overhead transparency…. Forget all that stuff about video quality….

The simple answer is: difference, relativity. No not the Einstein thing, just the property of being relative. White will look relatively gray with a way brighter white is right next to it, a brighter still white will make the 2nd white look relatively gray, sooner or later there’s enough difference the original white is now relativity black.

And if all you’re trying to do is demonstrate some math problems, perfect!

Ideally the room is dark, providing the black (or dark) areas in the image. If the projector is used in an area with ambient light then the black (dark) areas will not have as much contrast and the image will appear washed out. The same thing happens with every other display medium like LCD, LED and plasma screens, black is not created, it is already present.