Controlling the Color of Light (page 2)

Fluorescents

If you shoot video in offices, fluorescent light fixtures can cause a myriad of problems. When you white balance your camera to match the video lights you set up for your shoot, the fluorescent lights in the office will give surfaces a nasty green tint. You could turn out the office lights and just use your video lights, but that creates other problems such as a need for more fill light. Having enough fill makes the scene look more natural. What you can do is counter balance: either place an aqua colored filter in front of your video lights to convert them to the same color temperature of the fluorescents, or place reddish orange sleeves over the fluorescent tubes to convert them to the same color temperature as your video light kit.

Too Bright? Try an ND Filter

Sometimes, you may want to actually see the beautiful scene through a window as a backdrop. However, outdoor light is so much brighter than indoor light you would have to fry your talent to match the intensity. The answer? Neutral Density gels or ND gels for short. ND gels reduce the intensity of the light coming through the window while not changing the color temperature. They come in a variety of shades that are measured in the number of stops you want the light to be reduced. For example, an ND 3 filter reduces the light coming through the window by 1 stop. An ND 6 filter -- 2 stops. An ND 9 filter -- 3 stops.

If you want to combine a neutral density gel with CTO to convert the outdoor light to less intense indoor light, you can use a combination filter. While (to your eyes, anyway) it might appear that you have just placed a particularly nasty-looking brownish-orange film on your windows, your camera's image sensor will love it and will be dutifully capturing images of crystal-clear blue skies and lush, moist green grass.

The next time you go to a movie and see an office scene with the city shining outside the window, you can be assured that they have used color correcting gels.

Final Correction

While correcting the light from your lighting instruments or the windows is important, your hard work will only pay dividends if you remember to white balance every time you change positions. Even when shooting outdoors you can have a variety of color temperatures.

Take the time to white balance every time you change camera positions or directions. Remember, when your camera sees white as white, more than likely, the other colors in your scene will be right.

Robert G. Nulph, Ph.D. is an independent video/film producer/director and teaches video production courses at the college level.

[Sidebar: Are you Gellin'?]

Gels used for color correction for video and film production can be found at any theatre and video production supply store or on the Web. Do a search for "video color gels." The three major suppliers of gel are Rosco, Lee and Gamcolor. The filters come in 20X24 sheets, 20-inch by 24-foot rolls, 48-inch by 25-foot rolls, extra wide 58-inch wide by 24-foot rolls for covering windows (CTO and ND filters) and sleeves for placing over fluorescent tubes. These gels are optically clear. If you are very careful to avoid air pockets and creases when placing the CTO and ND gels over windows, you should not be able to see them in the camera.