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steve45
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How Does An Optical Projector Show Black?

04/18/2018 10:59 PM

After many years of watching various presentations, it dawned on me that I really don't understand how projectors work.

I recently sat through a slide show that had saturated black in the images. It was much darker than the edges of the screen that had no projected light striking it. I had never thought about it before, but figured that black would appear as just the absence of light from the projector. But, of course, this was not the case because it was BLACK.

So, how does a projector project a black image?
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SolarEagle
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#1

Re: How Does An Optical Projector Show Black?

04/18/2018 11:04 PM

..."Projectors do not project the color black. ... When a projector sends a beam of light on to a wall or a projector screen so that an image is formed on the wall or screen, the parts of the image that look black are really a very dim white color (which we sometimes call gray).Jun 16, 2015"...

..."Our human eyes and brains are designed to evaluate a color based on how it looks relative to the colors of the surrounding objects, rather than based on the absolute spectral content of the color."...

http://wtamu.edu/~cbaird/sq/2015/06/16/how-do-projectors-project-the-color-black/

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#2

Re: How Does An Optical Projector Show Black?

04/18/2018 11:11 PM

Ever notice how right before someone is going to use a projector, they dim the lights?

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jack of all trades
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#3

Re: How Does An Optical Projector Show Black?

04/19/2018 12:30 AM

I really want to say it uses a separate black light bulb.

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Tornado
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#4
In reply to #3

Re: How Does An Optical Projector Show Black?

04/19/2018 1:50 AM

The Journal of Irreproducible Results (there might be more than one issue of that zany mag) reported on the invention of the dark bulb.

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Relativity PL
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#8
In reply to #3

Re: How Does An Optical Projector Show Black?

04/20/2018 9:18 AM

Yeah, those black light bulbs are the only known emitters of dark photons:

https://en.wikipedia.org/wiki/Dark_photon
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rashavarek
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#9
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Re: How Does An Optical Projector Show Black?

04/20/2018 10:11 AM

Which is necessary to see dark matter right?

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Tom_Consulting
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#10
In reply to #9

Re: How Does An Optical Projector Show Black?

04/22/2018 4:58 PM

They only work if you have "dark thoughts".

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user-deleted-1105
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#5

Re: How Does An Optical Projector Show Black?

04/19/2018 4:14 AM

Same way as the old masters show bright luminous lights in a painting... one word.
Contrast!

Del

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steve45
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#6

Re: How Does An Optical Projector Show Black?

04/19/2018 7:59 AM

Thanks, Solar Eagle. I guess 'seeing is believing' even though it's an illusion.
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artsmith
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#7

Re: How Does An Optical Projector Show Black?

04/20/2018 8:52 AM

And don't forget, high contrast screens make a big difference, cw the old school "my living room wall" or basket of dirty socks.

Check it out:

http://www.dnp-screens.com/en/products/optical-technology/

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artsmith (1); jack of all trades (1); rashavarek (1); Relativity PL (1); SolarEagle (1); steve45 (1); Tom_Consulting (1); Tornado (1); truth is not a compromise (1); user-deleted-1105 (1)

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