Uploaded October 2017 | Updated September 2026, 1 week ago

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Want to upgrade your normal Schlieren setup to a color Schlieren setup? In this video, I'll show you how to quickly make a three-color filter out of flash filter gels (~$12, see link below) so you can get pretty pictures and videos.

Try experimenting with different color combinations (or number of colors) and post your pictures or videos!

===== NOTES =====
► I said that you'll see the green in parts that are undisturbed by any refraction, but you'll also see green when the gradient in index of refraction is zero. That's why the middle of the heat from the flame is green; you can think of it like the peak of a bell curve, where the derivative is zero because it's changing from positive to negative slope (or vice versa).

► The ideal size to make the middle filter (in my opinion as I'm writing this) is the exact width of the beam spot. This way, when there is nothing in the beam path, you'll only see green. If you make your middle filter too small, then your beam spot will be partly into the outer filters as well. By making the middle filter the exact size of the beam spot at the focus, you can be sure that any colors you see from the outer filters is due to an index of refraction gradient.

===== FLASH FILTER GELS =====
goo.gl/kv8tGd

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