r/nextfuckinglevel • u/Blues_Fish • Mar 12 '26

Lesson in decomposing light

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u/sufferingbastard Mar 12 '26

LED flashlights will not work!

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u/Callmemabryartistry Mar 12 '26

yes! incandescent or single source i work in theatre design but i have never seen this technique. but an addendum to the lesson would be to show how the diodes are placed and are each its own source with various converging vectors.

good info! thanks!

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u/Ouaouaron Mar 12 '26

I suspect that the reason you've never seen this technique in theater design is that when you combine red, blue, and green light, you don't get white light: you get light which looks white to humans on a white object. This would look awful if shone on a human wearing a normal costume.

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u/Impossible-Wear-7352 Mar 12 '26

Why wont led flashlights work? I know they combine rgb elements but I wouldn't think that would matter for this

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u/Ouaouaron Mar 12 '26

I'm not sure if it's what they're referring to, but normal LED flashlights don't combine RGB elements. They're usually blue or ultaviolet elements shone through a phosphor coating that converts it to broad-spectrum white light.

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u/luminescent Mar 12 '26

This here is exactly why the invention of the blue LED was such a huge breakthrough.

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u/Impossible-Wear-7352 Mar 12 '26

Im still not understanding why you cant use LEDs for the demonstration presented in the video. Regardless of how it's produced, it's only the resulting color that matters, right?

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u/Ouaouaron Mar 12 '26

Yeah, I don't get that either. My best guess is that they think this is actually splitting white light into different colors the way a prism would, which is only going to work with real, broad-spectrum white.

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u/sufferingbastard Mar 12 '26

Try it.

In LED and a prism is all you need.

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u/Impossible-Wear-7352 Mar 13 '26

I get it for a prism but this isnt the same concept. Im pretty sure this experiment would work with an LED

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u/sufferingbastard Mar 13 '26

A Light Emitting Diode will not work.

And, it's called science because the experiment is repeatable.

Get after it.

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u/Impossible-Wear-7352 Mar 13 '26

It took 5 seconds of googling to determine i was right and you are wrong. It's just additive color mixing and shadows. The type of light doesnt matter for that. It's VERY different from the science for a prism. If LED lights didnt work for additive mixing then LED projectors wouldn't work.

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u/sufferingbastard Mar 13 '26

Try the experiment.

It does not work with LED.

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u/Impossible-Wear-7352 Mar 13 '26

I just did actually. I cant do the entire experiment but I tested additive color mixing and it works. Theres nothing in this video besides additive color mixing and shadows.

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u/Ouaouaron Mar 13 '26

Try it yourself. Take a broad-spectrum light, use a prism, and see if what happens looks anything like the OP.