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Light Source: Working with Mixed Lighting

Light Source: Working with Mixed Lighting

Mixed lighting isn't necessarily a disaster. Here are some pragmatic solutions for your next location shoot.

"White" light ranges from the steely blue of outdoor open shade to the rosy orange of a household lamp on a dimmer. Your camcorder can produce a neutral white from any one of these different color temperatures, but only from one at a time. If you're lighting a location that includes, say, overhead fluorescent lights and halogen video lights, you face several problems. Some colors look accurate while others look too orange or too blue, or else the white balance is an uneasy average in which nothing looks quite right. Setups from different positions change the light balance. Subjects moving from point A to point B change color during the shot.

There are three different ways to cope with light sources that have conflicting color balances:

  • Turn their differences into an advantage.
  • Modify one or more of them by changing their color temperature.
  • Eliminate one or more of them by masking them or turning them off.

    We'll show examples of all three approaches, restricting ourselves to the three most common indoor light sources: window light, overhead fluorescents and halogen video lights. But first let's look at the lighting tools at your disposal and a basic strategy for employing them.

    Light Modifying Tools
    To modify the color of a light you can either gel it or replace it.

    To gel window light, you need sheets of orange gel (actually tough plastic film) large enough to mask the entire window. These sheets are available from professional video supply houses like Birns and Sawyer and from several of our mail order advertisers. Number 85 or 85A gels will usually match daylight to the color of halogen movie lights.

    Gelling a window is easy if the camera won't see the window, or if the outdoors will be out of focus - and if the window's on the ground floor. Simply hang the gel over the outside of the window, secure it with clips, and carry on. If the outer side of the glass is inaccessible, or if the window and its view must look realistic, you need to apply a special form of the plastic like auto tinting film to the inside - a difficult, finicky job. Better plan to frame off the window instead.

    Gelling a spotlight is a snap, simply fit a heat-resistant version of the gel in a circular frame and slip it behind the light's barndoors or clothes-pin a larger sheet across the open barndoors (this keeps the gel cooler). Blue number 81A gels are the classic tools here. If you have the bucks, dichroic glass filters are tougher and they help disperse heat from the lamp. You can gel a soft light by masking the light source inside the box (softbox) or covering the opening (broad). Treat really big lights like windows.

    Since fluorescent lights often hang above large ceiling grids, gelling them can be a real pain, unless you invest in tube-shaped corrective filters that slip on over the lamps. This solution works very well - unless the lamps and/or grid plastic have aged and changed color.

    Sometimes, it's easier to lower the river than raise the bridge: change the light instead of gelling it. You can carry a stash of sunshine-color fluorescents that are 90% accurate. Swapping them with the room lights takes no more time than gel tubes and far less than using gel sheets.

    As for "practicals" (room lights that will appear on camera) screw-base halogen lamps are available in most conventional shapes and sizes. To get perfect 3200K light, just swap your halogens for the house lights.

    A Basic Lighting Strategy
    Every lighting problem is different, but most problems will respond to the same working approach.

    First identify your different color temperatures. High-rent professionals will often use color temperature light meters to do this; but hey: you can tell window light, fluorescents and incandescents apart, can't you?

    Next develop your game plan. Which source will be your key light, supplying the dominant overall illumination? That decision will establish your basic color temperature. Then set color temperature manually, using a white card that reflects only your dominant light source. That light will now look subjectively white on screen.

    Now, get a wide angle on your set and check the results in a separate reference monitor. If you can't afford a studio model, a 13-inch AC/battery TV from Bigbox-Mart works fine. With the white balance set for the dominant color, what, exactly are your problems with the other color(s)? When you've determined this, decide whether you want to work with the different colors, modify one or more of them, or eliminate one or more.

    In showing you how, we can't cover every situation, so let's demonstrate with one of the most common ones: a room (class, meeting or office) with light pouring in through big windows, a ceiling grid of fluorescents supplying all the existing artificial lighting, and a light kit with two or three halogen spots and/or floods.

    Exploiting Multiple Light Sources
    If the ceiling fluorescents are new and of good quality, they may be quite close to the window light. (To check this, reset manual white balance while including both window and fluorescent lighting. If the overall effect on your monitor is pleasing, leave the balance that way.) You'll use the lower-source window light for keying and the high fluorescents for fill.

    If the high-position fill creates a Walking Dead cast on your subjects, try placing silver reflectors opposite the windows to use daylight for extra fill as well as for keying. Unless the reflectors must be too far away to work, the effect can be very pleasing. (And if they would be too far, use window and ceiling alone for wide shots; then move in reflectors for close work.)

    Now add halogen backlight. If it's not too intense, a splash of warm light on hair and shoulders can be very attractive.

    There: you've harmonized three different color temperatures without modifying any of them.

    Modifying Light Sources
    Often that's just not practical. At the very least, you have to blue-gel the backlight to match the windows and fluorescents. As noted, you could warm up the window and ceiling instead, but this is both expensive and time-consuming. So let's work with two sources instead by turning off either fluorescents or halogens, or by masking the windows with curtains or tacked-up painters' cloths.

    The quickest method exploits window and ceiling, with the daylight supplying the key and the ceiling the fill. Again, try adding lower-height fill with reflectors bouncing the daylight.

    Since the result may still have an old hospital corridor look, you may want to keep those video lights, with their greater versatility and ease of control. For one approach, try losing the ceiling grid. Key with the soft window light, blue-gel halogen fill lights, and go either warm or neutral with the back light.

    If the window light is not overpowering, and if you can mask it by closing the drapes or masking the opening, try working with the overhead fluorescents as fill light and gelled spots as multiple keys. This works especially well where the scene requires subject movement. The performers can move from one key light area to another, under a uniform fluorescent fill. Because the key lights are not much above eye level, you'll avoid that bus station glare. Don't block your subjects too close to their key lights or they will get too hot (both visually and thermally).

    Single-color Lighting
    Once in a while, you may choose to light your entire scene with a single light color. I once lit a large room with a bank of windows and only ambient bounce light for fill. The result had an extremely natural feel and the shadows didn't block up on me. If you do need more fill, try silver reflectors or large white cards.

    If you're making a documentary in a fluorescent-lit environment, you may need to standardize on overhead grid lighting. Its light is soft enough and the unflattering overhead position is acceptable as a super-realistic look. In this situation, be sure to reset your white balance as you move around, because fluorescents are maddeningly inconsistent. In bad conditions, reset your balance for every setup.

    Your last option is to turn your location into a studio. Drape those windows; kill those tubes, and light your whole show from your halogen kit. The advantage is control. Spotlights can be manipulated using focus, screens, barndoors and flags. Even softlights and umbrellas can at least be aimed.

    The big disadvantages involve setup time and power. The CEO's office doesn't have enough juice for many lights and the Big Cheese hasn't time to vacate the place while you set them all up.

    Besides, the general rule of thumb is to utilize ambient light where possible, shaping and augmenting it with video lights and reflectors. Unless you're a seasoned Hollywood gaffer, the result usually looks more realistic - and it sure takes a lot less time, equipment and power.

    Good shooting!

    [Sidebar: Setting White Balance - As Easy as 1-2-3]
    To set white balance:
    1)Hold a white card under the lighting in which you will shoot.
    2)Point your camcorder at the white card, filling as much of the frame as possible with white.
    3) Press and hold the manual white balance (WB) button.

  • Tags:  October 2003
    Jim
    Stinson
    Wed, 10/01/2003 - 12:00am