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Lighting Night Scene


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#1 Scott Frace

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Posted 13 November 2010 - 12:14 PM

I am planning on lighting a night scene outside our cities courthouse. I was planning on using a 8' helium balloon with a B&M 5K tungsten light bounced off it to created a soft glow, then fill in the front with a soft box and smaller lights where needed. The problem is the only generator I can get is a 6000w but only has two 30amp 240V outlets and six 20amp 120V outlets. If I have done the math correctly the 5K light is approximately 42amps running a 5000W DPY 120V bulb, which exceeds the 120V outlet max. Is it possible to change the bulb to a 5000W Arri CP29 220-240V and run it off the 240V line? This should bring the amps down to 22ish which the generator is able to handle.

I'm a student filmaker so HMI lights are out of the question. We have no rental places within 90 miles and no budget to work with. Is there another method to achieve the soft light look? I have several 1000w and 500w lights to work with. I'll be shooting with a RED one mainly 28mm, 50mm, and 85mm lenses, stopped down to f/4. Not sure if that helps with how much light I will need. Any help would be appreciated. Thank You.
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#2 timHealy

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Posted 13 November 2010 - 08:59 PM

That should work, but I would get the bulb and test it with your genny before your shoot to make sure your wiring works.

Having said that, I'm not familiar with a B and M 5k, but a typical Mole 5k would not be as punchy as a bunch of 1k par cans with 1000 watt narrow bulbs or 1200 watt fire starters.

I'm just saying.

best

Tim
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#3 JD Hartman

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Posted 14 November 2010 - 04:10 PM

Whats type of setting is the couthouse in? City, urban, sub-urban? What type of exterior lighting is already in place at the location? That should be the foundation to the lighting you wish to augment. What is the tone of the scene? If you have litle or no budget, wouldn't buying a 5000K 230V globe for the 5K be a poor use of that money? Yes, it's possible to get a 230V globe for that fixture.
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#4 Scott Frace

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Posted 14 November 2010 - 04:37 PM

Whats type of setting is the couthouse in? City, urban, sub-urban? What type of exterior lighting is already in place at the location? That should be the foundation to the lighting you wish to augment. What is the tone of the scene? If you have litle or no budget, wouldn't buying a 5000K 230V globe for the 5K be a poor use of that money? Yes, it's possible to get a 230V globe for that fixture.


The courthouse is in a city setting with only two large flood lights going up the front of the building. The scene being portrayed is a couple running out of a high society dinner after getting into a fight, so I'm just looking to have nice even light with a green wash on the building in the back. I will use LED wash lights that I have access to from a local DJ. As for the 230V globe, I have access to one from our school, for some reason they have an extra bulb laying around that we don't even have the fixture for.
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#5 Guy Holt

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Posted 15 November 2010 - 05:25 PM

That should work, but I would get the bulb and test it with your genny before your shoot to make sure your wiring works....Having said that, I'm not familiar with a B and M 5k


Even before you throw a 240V 5k globe in your B&M 5k to test it, you need to confirm that it has a double throw switch (switches both hot and neutral simultaneously.) If not you will have a hazardous situation where the lamp is energized without a return. You don’t want to become the return path to ground. If it does have a double throw switch you will also probably need an adapter to 4-pin 240V Twist-lock to plug into the generator because most 5ks are wired with a 60 Bates plug. A film rental house will probably have an adapter available

The safer option when it comes to running 5ks on portable generators is to use a 240v-to-120v step-down transformer to power a standard 120V bulb. A transformer will convert the 240 volts supplied by the 240V 4 pin twist-lock back to 120 volts in a single circuit that is the sum of the two single phase legs. A 6kw generator should be able to provide at least a 46 Amp circuit, which will be sufficient to power a 5k 120V globe since it draws 42 Amps. Unless the generator is one of our modified Honda EU6500is that puts out 7500 Watts you will not have much power left after the 5k.

You might be able to find a step-down transformer from an area tool rental house. It is not likely, however, a tool rental house will have one equipped with a 60A Bates receptacle, so you will likely have to provide them with a 60A female Bates pig-tail that they would wire into it.

For more detailed information on the use of step-down transformers I suggest you read an article I wrote for our company news letter on the use of portable generators in motion picture lighting.

http://www.screenlig...generators.html

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston
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#6 Scott Frace

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Posted 15 November 2010 - 11:46 PM

Guy,

I actually decided to go with the step down transformer instead of the 240V globe. My father is an electrical engineer at a nuclear facility and that's what he had suggested I do. He actually got a barely used 7.5KVa transformer from his work that we wired with a 60amp bates receptacle that I got from another local filmmaker. We powered the light up successfully off a 5500w generator with good results. I still haven't tried bouncing the light into the helium balloon but it seems like it should give me enough light to work with. I'll post pictures of the lighting setup from the set once I shoot. It's not until after Thanksgiving but just want to get all this figured out now. Thanks again everyone for all the help on this topic!
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