Beardy’s note: It’s Friday which means today we’re running Part 2 of Cinematographer Jeremy Applebaum’s excellent Three Part Guest Post about the basics of Low Budget lighting. And today’s installment is extremely helpful. If you’ve ever tripped a breaker during a big shoot, now you’ll know why. In case you missed it, here’s Part 1 of the Low Budget Lighting guide. And now, on to Part 2:
Part One: Calculating Amps:
In the first installment we went over the tools and gear you can pick up in order to build yourself a DIY, low budget light kit. This time we will go over some basic electrical safety. Before plugging anything in it is good practice to know where the fuse box is. And if it’s an older fuse box you’ll need some replacement fuses in case you trip a fuse. Even if you closely monitor your power draw, you never know when a refrigerator, furnace, tv, etc will kick on and blow the fuse. Any standard wall socket socket (circuit) can handle anywhere from 15 – 20 amps. In order to make sure you donʼt blow a fuse (or trip a breaker) you should always keep track of how many amps you’re plugging into the socket.
The formula for calculating amps is: Amps = Watts / Volts.
In America we use 120 volts. However, when calculating amps for my own shoots, I divide by 100, not 120 for a few reasons. One, itʼs faster: Itʼs a lot easier to and quicker to divide 500/100 (5) as opposed to 500/120 (4.16). Two, it keeps my amperage on the circuit down, further reducing my chances of blowing a fuse. While itʼs important to know that the formula for 100% accuracy, you can almost never go wrong with diving by 100 instead of 120.
Part Two Stinger Safety:
Something to keep in mind when handling power distribution for your scene is that stingers have gauges, which tell the amperage they can handle. Most off the self stingers will have gauges ranging from 12 – 16. But the longer the stinger, the less amps they can safety hold. Below you will find a chart explaining the differences (for America). If you are not careful your stinger can melt, causing a potential electrical fire.
As you can see it can get quite complicated if you’re running long stingers. You can never go wrong buying a higher gauge cord. In fact, unless you are really strapped for cash, you should never buy anything less than a 14 gauge stinger for film work. The same principle applies to surge protectors and to an extent, multi taps.
And now, some Bonus Questions! Answers to be posted at the start of next week’s article:
It should be noted that for the purpose of these questions volts are assumed to be at 120. It is perfectly fine (and recommended) to try solving these problems with volts at 120 and 100 (answers will be given for both). Stinger gauge/max amperage for the distance should be taken from the table above.
1: How many amps does a 500 watt work light draw?
2: If you have 4 500 watt work lights and one 100 foot 16 gauge extension cord, how many work lights can you safely power?
3: If you nearest 20 amp socket (circuit) is 50 feet away, you have a 50 foot 12 gauge stinger, and you need to power 20 amps of light could you safely power your lights?
4: If you have two 15 amp sockets (circuits), one 1,000 watt work light, two 500 watt work lights, two clamp lights with 100 watt lamps in them and two stingers, each 12 gauge 25 footers with attached multi taps could you power all your lights if the closest socket (circuits) is 45 feet away? If not how many more amps would you need?
Feel free to post your answers you may have below. Same goes for any questions you may have. Stay tuned for part three where we will go over a basic low budget lighting set up.
— Guest Post by Jeremy Applebaum. Check out Jeremey’s “Virtual AD” app here —