F2Bthere wrote in post #18636192
I don't use gels that often and don't see a lot of gells in most of what I look at.
They do matter in certain mixed light situations, but this doesn't come up a lot for most photographers.
I use gels from time to time. Usually, I suppress ambient completely and generate all light for the shooting situation, either with multiple strobes or with reflectors. This keep the color temperature consistent throughout. Just for fun, I just tried balancing xenon flash with overhead fluorescents. What a pain! Even with a Sekonic C-500 color flashmeter, it took forever. Gels are cheap and easy to use: just tape them onto the front of the flash, and special effects don't require critical color matching. Time for pics...
First, scary special effects.
Apparition created by my daughter, age 9:
Real background created by blue gel hitting a diffusion panel from behind:
Balancing the ambient shows fluorescents alone, then unmodified flash added, then flash color balanced:
Those are SOOC JPEGs. Below is the third image with luminosity and saturation curves, but color balance is unaltered.
The color balance was Rosco 3/4 CTO combined with Rosco 1/2 PlusGreen. 1/4 PlusGreen was not sufficient, so a complete pack of gels is good to have on hand. This Rosco 2"x3" swatchbook has at least 100 gels, and dozens of diffusion and reflector materials to inspect:
Not bad for $35.

Canon, Nikon, Contax, Leica, Sony, Profoto.