How to Use High-Intensity Discharge Lamps for Your DSLR Film
Artificial high intensity lighting for your DSLR video requires power to function, and when used for massive spaces, the need to make it both cost- and energy-efficient becomes important. That’s why high-intensity discharge (HID) lamps were created.
Instead of using heat to create light, they have a glass envelope (the glass tube part) where gasses are excited and produce light. But that light is created solely by this illumination and provides little or no benefit to your movie if you don’t understand how they work.
HIDs come in three basic varieties, each with its own behavior.
Lights effects with sodium vapor
Used primarily for streetlights, they emit a yellowish cast. You notice it when you study the street at night. They produce a colorcast that isn’t correctable because they don’t conform to a full spectrum of color. Instead, they correspond to a single wavelength.
If you were to correct it either by taking a white balance, using a blue filter, or taking out the yellow in postproduction, all that would remain is a monochromatic rendering of the subject. That’s because it only produces a single color of light.
Here’s how to make sodium vapor lighting work for you:
Remember that white balance doesn’t always work. If you slightly reduce the yellow in the scene, you’re still left with an overwhelming colorcast, but it can pass for a street scene, especially when you have supplemental light coming from store lighting, neon signs, and the red taillights of passing cars.
Shoot at twilight. This time of day still has ambient light and a purplish sky that looks great when you position your subject against it.
Light effects with mercury vapor
These monochromatic lamps (producing a single color) are less efficient than sodium vapor and far more problematic. These make light by exciting mercury in their glass envelopes, and they’re used for street lamps, parking lots, and other spaces where simple illumination is all that’s required. On average, they have a color temperature around 4,200K but only produce a cyan-greenish illumination.
Try these tips to capture movies under this illumination:
Don’t depend on manual white balance. Because the light doesn’t produce a full spectrum of color, the end result can produce a red-tinted or colorless appearance. Instead, try setting to tungsten and let it go warmer.
Use a UV filter. It can help counteract some of the dominance with colorcast. The colorcast won’t disappear, but you’ll be able to take the edge off.
Remember that it’s not flattering to humans. At least, not in the conventional sense due to its cyan-greenish colorcast. On the other hand, if you’re looking to depict something alien or evocative, it’s not a bad choice.
Metal halide lighting
With a mixture of mercury and metal halides excited in their tubes, these highly efficient, color-corrected lamps are designed to produce a full spectrum of color. They’re used for lots of situations, including stadium and arena lighting. Without them, you can’t have night games on television. Here are some tips for getting the best out of metal halide lighting:
Shoot at a slower shutter speed. With some lamps, capturing the scene with too high of a shutter speed may produce a colorcast. Using a 1/60 to 1/125 usually works fine.
Take a white balance. Depending on the specific type of lamp, color temperature ranges from 3000K to 20000K. Color temperature may also vary, even with the same type of lamp.