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Pattyjae 05-28-2011 03:24 AM

Extension cable length - Film Set
Hi everyone, I'm new to the forum. I am a film student a few weeks out from working on my final year film and have a few concerns about setting up lighting in a particular location.

The location is in rural Australia in an old shed on a farm. The closest power source is approximately 100 metres (328 feet) from the shed and I need to power a number of high wattage lights simultaneously. As far as I am aware, the power source (house) has two circuits, each with 5000W. Below is a picture of the power box, each circuit has 250V and 20A.

My question is this: is it possible to run a heavy duty extension cable (Or multiple cables) to the shed and still have useable power? Or is it just too far away to be realistic/safe? Are there any alternatives?

Our last resort is to hire a generator but as we will be shooting for close to a week this will add a significant cost to a very stretched budget and also provide noise issues. We will need at least 3000W usable power to create the lighting set-up desired.

Thanks so much!

Patrick Jaeger

kbsparky 05-28-2011 07:11 AM

With some good-sized extension cords, you should be able to utilise your existing power source. 100 meters is not too far away, considering your nominal voltage is 240. Even with some voltage drop, lighting is more forgiving than some other things.

I would not think that a generator is needed in this case.

AllanJ 05-28-2011 07:28 AM

One 12 gauge or two 14 gauge extension cords will result in a voltage loss no greater than six percent. This won't detract much from the lighting except that color temperature of incandescent ligihting will be affected. You should be able to compensate by changing the white balance for digital shooting. However, using film, if you use filters to correct the color temperature then you may need more light which in turn will require more power.

kbsparky 05-28-2011 08:04 AM

I don't believe that they use AWG wire sizes in Australia. Our down-under friend here will probably need a metric equivalent.

Pattyjae 05-28-2011 11:18 AM

So if I get the Australian equivalent of a 100m 12-gauge extension cord, there will only be a voltage drop of 6% overall? Does this increase with cable length?

6% of 250V is 15V, so I would have a voltage of 235V at the end of the cable run, thus only losing 50 degrees kelvin in colour temperature (Based on 100 degrees lost for every 10V dropped and the Australian voltage being at 240V)?

How much wattage would I have at the end of each 100m cable run?

Perry401 05-28-2011 12:15 PM

In my youth, I worked assisting with lighting on a number of student and professional films. Lighting was always an issue. It doesn't seem to matter how much light you think you will need -- you always need more.

The color-shift issue on film should not be an issue if you are having prints made from the original film stock -- they can compensate for minor color changes in the printing process (called "timing" the print). Also be sure to use a film rated for artificial light use. Adding filters to the camera only cuts down on light to the film and therefore the need for more lighting.

You can also contact your film lab (again assuming you are using film) to find out methods to "push" the processing to let you film with less light. This will create a more grainy image however.

One obvious help is to paint all possible walls and ceillings in the place you are shooting with white or very light colors. You can also get rolls of constuction paper like materials that are something like 2 meters wide and perhaps 10-30 meters long. These can be stapled or taped up as temporary reflectors.

If you intend to work in film for a while, I would suggest buying "good" 12 gauge extension cords -- perhaps in 50 foot lengths -- which you could use again and again and arrange in different ways as needed for future shoots. I have seen students buy UF cable and make their own extension cords, using top-of-the-line plugs and sockets. These have the disadvantage of being stiff since they are single strand, and being a home-made assembly, they might not be covered if there was some sort of an accident caused by them.

Renting a generator may not be that good of an idea if you are using sound -- the generator will most likely be audible even if several hundred feet away from the filming sight. I always pushed for using an existing power source whenever available rather than a generator. You might contact a local electrician and have him set up a temporary feed from the main building to the filming sight. This might be cheaper than renting a generator.

You might also check the output lumes vs. wattage of the lights you are using. Some bulbs have short lifes -- perhaps only a few hours -- but up to double the light of other bulbs which last longer. In your situation, you might find the cost to relamp several times during the shoot is cheaper than buying more extension cords or needing to get a generator. Using dimmers that have a full-power position and setting the bulbs dim during non-filming activites can help the length of time the bulbs last. Many bulbs fail on initial power-up and turning the lamps on and off can cause them to fail more quickly. Often lighting can be arranged with half or even lower intensity, and need only slight adjustments when the bulbs are turned on to the maximum position.

Some flourescent lights have outputs in the 3200-3400 K color spectrum. These are not usually sufficient to use by themselves, especially for flesh tones or critical color applications since the color phosphors will create a non-linear color balance, but sometimes these can be used for lighting walls or other backgrounds where slightly goofy colors might be acceptable. Just remember that low-frequency or line-frequency ballasts might produce strobing or other undesireable effects. High-efficiency solid state ballasts are generally better for film and video work. You should shoot some test film or video with any non incandescent or halogen light source you might want to use to see how the results look.

Of course in an extreme case, you could do like Edison and other early film pioneers did, and cut a hole in the roof to let natural light in!

AllanJ 05-28-2011 02:10 PM

I am guessing that the wattage drawn by the lamps will be slightly greater after the voltage drop has been suffered. At a lower voltage the lamp filaments will be at a lower temperature, their resistance will be slightly lower, and the number of amperes will be slightly greater. Some of this greater wattage will have been consumed in the wires so as to result in the voltage drop.

Selected solid wire sizes:

AWG 16 gauge -- 0.051 inch diam -- 1.29 mm diam -- 1.31 sq mm cross sect.
#14 -- 0.064" diam -- 1.63 mm diam -- 2.08 mm2
#12 -- 0.081" diam -- 2.05 mm diam -- 3.31 mm2
#10 -- 0.102" diam -- 2.59 mm diam -- 5.26 mm2

Longer cables of the same size means proportionately more voltage drop.
For incandescent lamps with critically short life times at full brightness, the life time is lengthened at the lower voltage as a result of voltage drop in the wires.

frenchelectrican 05-29-2011 02:03 AM

Allen I will post the common mm˛ size real quick due the Aussie and Europeans are use the same cable size.,

14 AWG = 2.5mm˛
12 AWG = 4.0mm˛
10 AWG = 6.0mm˛

Common colour code we use in both Aussie and European { per current codes }

Brown - phase conductor
Bleu - Netural conductor
Green with yellow stripe - Earth or Terra or Ground { three words will result the same function }

I am not too sure about Aussie regulation but I am pretty sure they will required RCD { simair to the GFCI in USA/ Canada side } I know for fact France must use the RCD for portable outdoor luminaires.

for 100 meter distance the 4.0mm˛ will handle it ok with 20 amp breaker as long the indentscent luminaire have some degree with voltage drop issue but for HID or any other ballasted loads it may or may not affect { I know older one were rated for 220/230 volts so they should not have issue with brightness and colour tempture }

And I will suggest that you should have a electrician to assit you on the RCD hook up due some are little tricky to deal with it.


Pattyjae 05-29-2011 04:53 AM

I like the idea of having an electrician set up a temporary feed from the house to filming location, would they be able to cover the distance without any/minimal loss to the output? Is it a complicated process? (Trying to get an idea of cost)

I am shooting digital on a fairly decent camera so will have a fairly high sensor sensitivity with minimal noise. How low could the colour temperature drop? I will be dropping CTB gels over the lights for the night scenes anyway so a little more gel could help get the temp back up. Otherwise I could always just set the temp lower, at around 3000K, but this all depends on how much the temperature can drop.

I will be using a few fluorescents, just Kino flos though so I would assume that they won't present a problem as they're designed for film lighting.

"for 100 meter distance the 4.0mm˛ will handle it ok with 20 amp breaker as long the indentscent luminaire have some degree with voltage drop issue but for HID or any other ballasted loads it may or may not affect { I know older one were rated for 220/230 volts so they should not have issue with brightness and colour tempture }

And I will suggest that you should have a electrician to assit you on the RCD hook up due some are little tricky to deal with it."

Sorry, I don't understand most of this. Are you able to simplify it for me :)

Perry401 05-29-2011 06:17 PM

Pattiejae --

My experience with electricians hooking up temporary feeds has been pretty good. Anyone who does much work will have the knowledge and some left-over materials from other jobs or salvaged materials they can use for the temporary service. They might, for instance, hook up what we call a service drop cable to the sight. In the USA, there are provisions in the NEC (National Electrical Code) which permit temporary wiring for situations such as yours, or for things like carnavals, construction, and similar situations. A well versed electrician, with some materials on hand should be able to get you hooked up for an affordable amount. After your shoot is over, he/she will take his/her materials back, so you are in effect renting the wiring devices and paying for his expertise and labor to put up and take down the system.

Several of the semi professional and professional jobs I worked on gave acknowledgement in the film's credits. "Special Thanks to Acme Electric for Their Help and Support in the Making this Production." Some mid-sized firms did the work for "free" in exchange for the publicity and since it was a school-related job, they could take a charitable contribution deduction on taxes, or write the charges up as an advertising expense.

frenchelectrican 05-29-2011 07:17 PM


Most flourscent are useally not super senstive with voltage drop as long the ballast { it will look like either black or white brick like block which it will control the current to the bulb itself } ditto with HID { high indensity discharge } simauir to large Metal halide spotlite they used common used in movie set.

For the distance as I stated the size it will handle without major issue as long you keep it under 3 kilowatts load per circuit otherwise a good electrician will set up a tempory subpanel or subunit to distubated the load for the rest of the luminaires or other equiment you will need to use in the movie set.

Again as I mention have a electrician come out and help you on this one to be on safe side I know some may charge you and some may don't depending on what size of movie set up it will be as Perry mention not too long ago on that comment.


Pattyjae 05-31-2011 06:10 AM

Perry, that is quite a good idea. I'm planning to call a bunch of Electricians close to the shooting location tomorrow so hopefully it all turns out well.

Thanks FrenchElectrician. The Kinos we are hiring do have ballasts so from what you've said I'm now feeling more confident in them.

Thanks so much for everyones help! :)

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