Basic Training: Looking for Light

Kyle Cassidy
January 2007

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One of the inherent problems in shooting in "low light" is that there is no real definition for what low light is. Some people may consider anything darker than a cloudy day to be low light. To others, a sixty-watt bulb in an overhead socket may be low light, and to a Special Forces team in the desert, starlight may be "low light." These definitions and the solutions to shooting under them all hinge upon what you expect to get from your video. A police surveillance tape has different goals than a feature film. The second difficulty that you'll run across in "low light" shooting is that camera manufacturers can (and often do) use arbitrary methods of determining their products' capabilities.

There's a very complicated definition of how light is measured in LUX, but the basic rule is that a 1 LUX camera will be able to achieve an acceptable image lit by a single candle from three feet away. What's "acceptable" varies from one camera manufacturer to another and from one use to another as well.

The Electronic Industries Association has come up with a standard called EIA-639 that seeks to hold everyone to the same rating system, but at the moment it's voluntary. So, it's possible that you have camera manufacturer "A" saying that an image is acceptable at a level of light that another manufacturer doesn't think is acceptable. So, if you're buying a camera for its low light capabilities, spend some time reading the reviews before you believe what's on the side of the box. Understanding all that, here are some tips for shooting in low light.

This may seem obvious, but it's continually ignored in practice. Before grandma opens her present, for heaven's sake, open the blinds, let a little light in. If it's possible, move your subjects to a better location. Use a flashlight, use car headlights, use a cardboard reflector. Just because it wasn't advertised as lighting for video production doesn't mean that it won't light your video production.

The f-stop or "aperture" is a variable diameter ring (iris), which controls the amount of light that hits your camera's CCDs. The wider the iris, the more light passes through to the imager. To make it confusing, a wide f-stop is designated by a smaller number. Aperture position f/2.8 lets in more light than f/8. An easy way to remember this is to think of aperture as a fraction, where 1/2.8 is a larger opening than 1/8.

You can also control how much light makes it onto the frame by increasing the amount of time that the CCD is exposed to light. There is no actual physical "shutter" on a common digital video camcorder's CCD, but light falling onto it is aggregate; the longer the electronic shutter is active, the more light it's collecting. This works just like a mechanical shutter. Typically, video cameras operate at very close to 30 frames per second. For stationary or slow moving subjects, 15 frames per second might still produce an image with acceptable levels of motion blur. When you do this, you should mount your camera on a tripod.

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