http://www.leefilters.com/lighting/colour-list.html#
I use this all the time. And attached is my current list of gels I use besides the usual stuff you find on the truck like 250,251, light grid, CTO and CTB
Diffusion -I use opal a lot. Hampshire is nice for a slight effect. Grid cloth is great for heavier needs. 250/251 are standards. Color temp - I always keep 1/4s and 1/2s of them. I don't know why, but I stay away from full ctb or cto. Minus green is a must if you are using less expensive LEDs. 1/4 usually does the trick.
I also like straw, pale gold, the steel blues, chocolate, along with some cosmetics - salmon and peach etc...
When I started building my own lighting kit, my rule was that I wanted to make sure I owned any gels that I had heard mentioned enough times on a set that I had come to know what they were. 215, 216. Opal, CTB, CTO, etc. Later I added whatever gel I had desperately wished I'd had from my most recent shoot. At the moment I have a few tubes I work with: diffusion, CTBs (in various strengths), CTOs, +/- Greens, Cosmetics, and Party Colors. With gels, you're going to end up using the same few all the time, but when you have just the right weird gel when you need it, it's so great.
Sometimes I buy gels hoping I'll have the chance to use them someday because they're so cool. Most of these are still unused.
Diffusion is the only one I know that's worth buying on big rolls. A really big piece of diffusion is great and often you'll just hang the roll from a C-stand arm and then roll it back up at the end of the setup.
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