The Indie Auteur Musings on filmmaking by Stephan Vladimir Bugaj.

Lighting Locations: You’ve got the power

There are several issues with lighting a location (and by a location I mean “somewhere we found in the world” vs. “a professionally maintained filming venue”).

A big one, and the one that this post is about, is the availability of electrical power. Not only do you need to worry about where the outlets are, you also need to know how many circuits you have and what the voltage and amperage is.

For low/no-budget shooters in the United States, you’re almost always dealing with 15ampere 120volts alternating current (15A 120vac) household circuits. Occasionally, you’ll run into 20A 120vac, and less frequently you’ll run into 220vac power (usually 220 is found in homes for powering clothes dryers), and only in industrial sites are you likely to run into 440vac and other exotic power types. Unless something has gone horribly wrong (and is not up to code), an outlet that looks like what you’re familiar with in your house should be 15A or 20A 120vac. (If you don’t know how to figure out what kind of power you’ve got on your hands, and how to hook up to it, consult a professional. Electricity is dangerous.)

Since Watts = Volts x Amps

One of these 15A 120vac circuits can take 1800w (real watts, see below) of lighting (though you should really come in under that since you probably don’t really know the quality of the wiring at the location). So, if you have some Arri Fresnels for example, you could put a 1k and two 300s on one circuit, or you could really push it to the limits and put three 600s on it.

How many Amps you’ll use is Watts/Volts. So for 120vac, here are the values for common lights:

To keep your equipment especially safe, try not to go over 13A on a 15A household circuit, whenever possible. (Or 18A on a 20A household circuit.)

Whenever you’re dealing with real wattage ratings, these calculations are always true. However, some lights (particularly non-professional flourescent replacement bulbs for tungsten household fixtures) print a wattage rating on the packaging and/or bulb that is a tungsten equivalent wattge. This is because most people are unfamiliar with footcandles, lux or lumens @ X meters as measures of brightness, so they want a bulb “as bright as XXX watts.” You should make sure you either have the real wattage, or locate an amperage draw rating, for any light that’s not a professional tungsten light, HMI. (NOTES: HMIs: take up to 150% of their power draw to fire up the ballasts, so up to 1200w HMI is all you should put on one household circuit. As for Kino-Flo flourescents, they are rated at fewer amps than their model numbering might lead you to believe. The Diva 400, for example, is rated at 2A in their literature. This is because the model 400 is actually 4 55watt flourescent bulbs, for 220watts (1.83A). The Diva 400 is also cited as having the illumination equivalent of a 1kw tungsten lamp, so the 400 numbering seems to be based on just the max # of bulbs and not wattage or tungsten equivalent wattage.)

Also remember that your camera, sound equipment, work lights, etc. also draw power. You need to figure them into your load calculations if you’re putting them on the same circuits as any of your lights (which, by the way, is not recommended).

Sometimes your location has no power, or lousy power. Then you need a generator. If you’re bringing a generator, even a home / industrial / farm one you rented from a hardware store, remember to find out how many amps the circuit in the generator is (and how to set the generator to 120vac if it’s not always set to that by design). Many generators have the amperage information printed on the housing near the outlets, and either an obvious 120v/220v switch or a label saying the generator is 120v or 220v always. But if yours doesn’t have such helpful information and controls in an obvious location, consult the operator’s manual before hooking your expensive lights up to it.

Running long cables can lead to problems stemming from voltage drops. A more comprehensive understanding of that issue is perhaps for a future post, but the rules of thumb are: always use the heaviest (lowest gauge number) and highest quality wire you can afford, and try to avoid runs longer than 100 feet. If you need to get a generator really far away for sound purposes, make a trip over to a grip house and inquire about quieter generators and/or power cabling that’s rated for very long runs. However, test out a few cheap options first. I’ve recently discovered that a small, late model Honda generator placed at about 50 – 100 feet from the set is pretty quiet to begin with, and can be made quieter by hiding it somewhere clever (outside — definitely not in a building or vehicle).

Also, do not assume that when you find two outlets at your location it means two circuits (even outlets that seem far apart may be on one circuit). You need to actually test this. The easiest way to do so is to own a few circuit testers (they’re about $12), put them in the outlets to see which are live (a good idea to begin with), then get permission from the person in charge of the location (not your location manager, the person who let you shoot in that location to begin with) to switch off the circuit breakers one-by-one and have someone on the crew mark down which ones go out at the same time.

Lastly, remember to tape down your power cables with gaffers’ tape, and weigh down C-stands and light stands with sandbags. Keep your set as clean, safe, and well organized as possible.

Knowing enough about power management on-set to keep your cast, crew, and equipment safe is absolutely essential, even for a low/no-budget production. If you have any sense, you’ll refuse to work on any set where it isn’t the case that the person in charge of gaffing (lighting) knows this stuff.