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Tuesday, June 7, 2011

Cool Lights

HMIs, LEDs and fluorescents are energy-efficient alternatives to hot lights for digital stills and HD video

This Article Features Photo Zoom

Bron Kobold Lumax SB24

Kevin Crawford, VP Engineering, Frezzi Energy Systems, notes, "You can set up stackable LED arrays for a nice wash of light, but it's not very cost-effective compared to a single-source 400W HMI projected through a 4x4-foot silk."

Equally important, large LED arrays come with large heat sinks because heat is, indeed, generated—only toward the back of the fixture. The result: a heavy and cumbersome fixture. The efficiency of that heat sink, in part, determines the life of the LED, which may be reduced to half its nominal life of 100,000 hours. Still, 100,000 hours isn't a bad run—that's over 4,000 full days, or 11.4 years of constant use.

What's especially appealing about LEDs is that many fixtures offer a choice of color temperature settings from tungsten to daylight or beyond on either end of the scale—on the fly, without resorting to filtration. However, some fixtures may instead be designed to accept gels. Adding diffusion may be another option.

If you need a true soft light source, without adding any modifiers in the light path, the obvious choice is a light bank comprised of fluorescent tubes. This bank would consist of anything from two to as many as six or eight lights. In fact, Frieder Hochheim, president and founder, Kino Flo, observes that he'd used a bank of this nature (four-foot tubes in a four-light array) as a beauty light. "I first used it on Faye Dunaway in the movie Barfly. It became 'her' light—she immediately recognized the soft, wraparound quality."

Many fluorescent tubes come in a choice of color temperatures to match an existing milieu.

When it comes to CFL (compact fluorescent), Hochheim outlines that CFL is a generic term that the lighting industry uses to differentiate narrow-diameter glass fluorescent tubes from the earlier wider-diameter lamps. "CFLs are brighter and smaller than the older linear-type lamps and far more energy-efficient," he says. "They can be spiral, linear or twin-tube linear with a single lamp base. The term 'Biax' is a GE marketing term identifying their twin-tube CFLs; Philips calls theirs PL-L; and Osram refers to them as Dulux L Lumilux De Luxe."

In The Final Analysis

Kino Flo's Hochheim offers this observation, "It comes down to, is this fixture going to do what I need it to do? I need to light an area six feet wide or whatever; what am I going to use? I can use six LED arrays stacked together, or I can maybe use one fluorescent fixture. That's what starts dictating people's choices over one or the other. In the end, I have to decide what delivers the lumens I need over a given surface. Very often, the best light is what is right for the shot. For this reason, it's important to have high-quality sources that can coexist within a shot and not reveal themselves through mismatches in color."