Lighting Gels (page 2)
Make Sure You White-Balance!
We all know that, when a camera sees white as white, the rest of the colors in your shot should be correct. However, what if you are using colored gels? Remember, if you are using a blue gel to create bluer light, you actually want to see it as blue. If you white-balance under the blue light, the camera will think it is white light, and it will turn everything orange. When using colored lighting gels, always make sure you are white-balancing with the white light that you are using to light your talent. If you want to light your talent in blue light, to look as if they are walking through moonlight, then you must remove the gel, white-balance and then replace the gel.
Color-Correction Gels
While there are more than 30 color-correction gels you can use to change the color temperature of a light source, they all fall into four major groups: CTO, CTS, CTB or Plus or Minus Green.
CTO, or color temperature orange, is a gel that you can place over windows to convert outdoor 5600K light to indoor or 3200K light. In other words, it strips the blue out of the outdoor light so that it will match the color of the indoor light.
CTS stands for color-temperature straw. This gel has the same function as CTO, except that it is more yellow and less red. This provides a little cooler color for outdoor light.
CTB, or color temperature blue, converts 3200K indoor lighting to match the 5600K light coming through the windows. This is a very effective gel that enables you to use outdoor light as your base light, while you use a 3200K instrument gelled with CTB as your key light.
Finally, Plus and Minus Green gels are used to color-correct fluorescent lights. The Minus Green gels are magenta in color. They strip the green out of the fluorescent light and match it to indoor or 3200K light. If you find that you are spending a lot of time shooting in offices with fluorescent tubes, you may want to buy tubes of Minus Green that fit over the fluorescent fixtures.
Neutral Density
One final word on lighting gels: If you are using CTO or CTS on Windows, you will probably still need a neutral-density filter to decrease the level of light coming through the window. Outdoor light is much brighter than indoor light, and the neutral-density gel reduces the light coming in without changing the color temperature of the light. Conveniently, gel manufacturers have combined the CTO and CTS gels with neutral-density gels, so that you can actually use one gel to accomplish both color correction and light intensity reduction. Your windows will look like they have a brown glaze, but the camera will see only the beautiful green grass and blue skies that lie beyond the windows.
Contributing editor Robert G. Nulph, Ph.D., is an independent video/film producer/director and teaches video production courses at the college level.
