Just bought Lights... Have some Questions

Zblock

Zblock

Well-known member
So I'm been reading up on lighting for awhile and looking to buy a kit for a few months.

I've shot a bunch in the last 6 months and really thought I was ready to spend some money on lights. Today I purchased 3 650watt's with stands and barndoors.

I set everything up at my place and did some camera tests.

Can anyone say about how many of these lights can be plugged in before a house breaker blows? I know thats a real specific question but my last experience would say that 4 650w's would flip one. Can anybody throw me a number?

Can I buy any old softbox for these or does it need to be specific. There's a LOT of heat coming off so do I need a Non flammable softy? Do you take the barn doors off when you use a soft box?

I don't really even know why I'd use the barn doors. The light is Soooo bright I think I'd have to soften it up anytime I pointed it at an actor. That kinda defeats the purpose? Should I move them farther away in order to Light an actor? How do you guys justify that much light on a characters face?

Do you usually diffuse the light with a gel or something else or is there a lot of shots that just use the open lamp?

I'm experimenting so I'm sure I'll be able to answer some of these questions in the next week but I'd appreciate the feedback and I'll post what I find out.
 
Can anyone say about how many of these lights can be plugged in before a house breaker blows? I know thats a real specific question but my last experience would say that 4 650w's would flip one. Can anybody throw me a number?
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Four 650's will flip any circuit and may even present a fire hazard.

Most modern houses are wired with 15-amp circuits, some have 20-amp. On a 15-amp circuit you could support a maximum of about 1800 watts, if the wiring is in great condition and there's absolutely nothing else drawing power. So, with 650's, that means two on a circuit, max. On a 20-amp circuit you could maybe get away with using three of them, but that's pushing it.

Now, keep in mind I'm not a licensed electrician, so what I say is general usage observations and not specific qualified electrical advice.

You really shouldn't ever count on getting the full theoretical draw from a household circuit anyway. A circuit could be interconnected with other outlets that you wouldn't expect, there could be a difference between the wall circuit breaker rating and the actual wiring that's inside the walls (i.e., they may have put a 20-amp circuit breaker in the box, but wired the outlets with wiring that only supports 10 amps... sure, that doesn't meet code, but who knows what people have been doing in their houses?!?!)

If it's a new or pretty modern house, it should have 15-amp or 20-amp circuitry, and decent wiring. If it's an older house, all bets are off, and you had better be paying attention to the walls (occasionally feeling them to see if they're heating up, due to too much resistance in the wiring in the walls).

I advise you get plenty of extension cords and spread those 650's around on different circuits. You can usually find different circuits in bathrooms or the kitchen, sometimes they'll split the lights in a two-story house so the upstairs is on one circuit and the downstairs on another, etc. Spread the load around and you're far less likely to run into any issues.
an I buy any old softbox for these or does it need to be specific. There's a LOT of heat coming off so do I need a Non flammable softy?
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You definitely need one that's designed for video, not for stills. There are still-photography softboxes out there that aren't designed to deal with the heat from a continuously-operating light source. Still boxes work with strobes (flashes). Video softboxes are designed to deal with the heat from a continuously-burning tungsten lamp. Don't cheap out, definitely get the right box for the job.

Do you take the barn doors off when you use a soft box?
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Of course. Barn doors slot into the accessory tabs on the front of the light, and so does the softbox's speed ring, so when you have a proper softbox the attachment will be obvious and you'll know that the barn doors come off.
 
Thanks Barry. I searched a bit more and found a useful table that echoes what you just said.

[FONT=Arial, Helvetica, sans-serif][SIZE=+3]Powering up the rig[/SIZE][/FONT]
[FONT=Arial, Helvetica, sans-serif][SIZE=+2]Important: [/SIZE][/FONT][FONT=Arial, Helvetica, sans-serif]MOST POWER POINTS CAN ONLY YIELD A MAXIMUM OF 2400 WATTS, EXCEEDING THIS VALUE MAY CAUSE A CIRCUIT TO TRIP OR MAY EVEN CAUSE A FIRE HAZARD. [/FONT][FONT=Arial, Helvetica, sans-serif]Make sure you do not connect more than 2400 watts of lighting to a single power point. Before you power lights up, do a quick power calculation, add up the wattage of the lights you are going to use. Use the following table as a guide.[/FONT]
CURRENT CALCULATIONS Light Types Power Rating Key Light 650 WATTS Back Light 650 WATTS Fill Light 1000 WATTS POWER TOTAL 2300 WATTS Table L1.


I guess it's suggesting you could power 3 650w's off the same circuit but from past experience you're on a time limit using that much juice. They'll run for a few minutes until things get warm and then shut down.
 
If I remember the math right:
Amps = watts/volts
or
Watts = Amps x volts.

So your 650 watt lights are pulling right at 6 Amps. I have a few 650 open faced lights and have used them for a long time. I would not try to run more than two of them off of one 15 amp circuit.
As for using the lights, I would rarely use a 650 open faced light as a key light for portraiture, except in very special circumstances. I like bounced light and use foam core or poster board to make a soft source. you can also get a soft box to make a soft source. The commercially made soft boxes, if rated for the wattage of light you are using should be safe. Yes, moving the lights farther away from the subject will lower the intensity of the light. Light is subject to the inverse square rule, which means if you move the light twice the distance away, you cut the light intensity to 1/4. Here is pretty good article about that.

http://www.microfilmmaker.com/tipstrick/Issue12/light1.html
 
Usually people will just do paper amps. It's good because it's easier to calculate, but it also gives you a bit of a safety margin in there.

Just divide the wattage by 10. So a 650 would be 6.5 amps. If you're really stuck for power you can start figuring out the actual wattage, but most of the time paper amps will suffice.
 
Zblock said:
I guess it's suggesting you could power 3 650w's off the same circuit but from past experience you're on a time limit using that much juice. They'll run for a few minutes until things get warm and then shut down.
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But that presupposes that you're using a 20-amp circuit. Not all household circuits are 20 amps! Many, many are 15 amps.

My advice is: don't push it. Spread the load around. Get some of those heavy-duty orange extension cords from the home improvement store, and put no more than two of your lights on a circuit, and you should avoid problems in almost all cases.
 
Yes, many circuits are 15 amps and ALL edison outlets are 15 amps. Never plug more than 15 amps into a standard wall outlet.
 
Thanks guys. Lol I'm running out of storage room for my film stuff. I've already had to stow my dolly and tools at friends places.

I DON'T want to be the one who spends all this money on gear which sits around and then someday selling it wishing I would have put it to use.

Hoping to shoot one more big project before June. Then it's 6weeks 15,000 mile roadtrip time and then back to LA and hopefully getting right back into it. With that said, if anybody in LA needs to use the lights between now and the end of May I'd be happy to bring them and learn a little on set.

Thanks for the answers.
 
First thing when getting to a location: open the fuse box, if it's in an old apartment like mine you will get 1x 15AMP (i'm not kidding you!), on more modern houses you get a variety of switches with numbers 15 or 20 (AMPs), for the simplicity sake (and safety) :
15 AMP = 1500w max
20 AMP = 2000w max
 
Amps is calculated at 10percent to the watt value. So 650w frennel is equal 6.5 amps as a general rule. Now when you go into location, I first go to the fuse box and check out what fuses is being used and note the amperage for each breaker. Then go and buy a bunch of replacements in case you blow some when shooting. Especially in a old house. To figure out which lines are to what fuse, get a portable light and plug into a outlet. Then start testing each switch till the the light goes out. and label it (A). Then continue around the room labeling all the (A) lines. If you come across a different line label (B) and etc. The best source is near the kitchen, bathroom and laundry room. Then try to restrict the number of amps are used for each line. For instance, if you have 3 outlets use the same line (A), then no more than two lights could be used on a 15amp fuse. If it is a old house I only put one light per line. If you use extension cords, use heavy duty ones and never coil them up tightly or you will burn a whole in the carpet. Keep it well ventelated. I personally use 650w openface arri's with barndoors. Then I use wooden clothes pins (c_47's) and attach my gels on to the barndoor in front of the light. Be it CTO's CTB's or Diffusion.

PS...Turn off all computers and unnecessary electronics on the line, If you blow a fuse, the computer will shut off.
 
phudsontx said:
Yes, many circuits are 15 amps and ALL edison outlets are 15 amps. Never plug more than 15 amps into a standard wall outlet.
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I put 2k's into standard wall outlets all the time and they're around like 16. Just be sure that you know what a 20 amp circuit and what a 15 amp circuit is.
 
Alright, math nerd time, sorry, but I saw it come up twice. Divide wattage by 100 not 10. The results stated are the same. A 650 watt is 6.5 amps, but 650 divided by ten is 65 not 6.5. So amps are 1% of wattage.

actual amps=watts/voltage so a 650 (technically) is actually more like 5.42 amps, but dividing by 100 is easier to do in your head and gives you leeway so you don't round something down and blow a circuit.

Not to call anyone out for bad math, I just wanted to set it straight for new guys looking for info.
 
It's a simple Ohm's Law calculation.
P(power in watts) = I (current in amps) X E (electromotive force in volts)
If you know any two, you can solve for the other.
In this case, I (amps) = P(watts) / E (volts).
Household outlets can vary anywhere between 112-130 volts which makes a difference in the maximum current draw for a particular circuit. Usually, ......thats "usually", the nominal outlet voltage is 120v. So 650w/120v = 5.4 Amps. Assuming no other loads on the circuit, three of those fixtures would draw 16.25 Amps.
If your outlet voltage is 112v, your current draw from a 650w lamp is 5.8 amps!. Three of those would draw 17.4 amps. If your outlet voltage is 130v, your current draw from a 650w lamp is 5 amps. Three would draw 15 amps.
As others have said, the age of the house is an important factor. Given the age of your circuit and the exact voltage at your outlet, your mileage will vary.
 
smithy said:
PS...Turn off all computers and unnecessary electronics on the line, If you blow a fuse, the computer will shut off.
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One thing to watch out for is the large appliances, like the refigerator, kicking on during the day, with lights on that circuit. The sudden surge can kick out a breaker (besides being heard on the sound track in many cases). So turn it off also. The real hard part is to remember to TURN IT BACK ON when you are done. One trick I have heard is to put your car keys in the freezer, so you can't leave without going to the 'fridge. I put a big note on the fridge saying to turn it back on so that when I do my idiot walk, I can make sure I don't forget.
 
Mister Stocks said:
Alright, math nerd time, sorry, but I saw it come up twice. Divide wattage by 100 not 10. The results stated are the same. A 650 watt is 6.5 amps, but 650 divided by ten is 65 not 6.5. So amps are 1% of wattage.

actual amps=watts/voltage so a 650 (technically) is actually more like 5.42 amps, but dividing by 100 is easier to do in your head and gives you leeway so you don't round something down and blow a circuit.

Not to call anyone out for bad math, I just wanted to set it straight for new guys looking for info.
Click to expand...

Good catch!
 
Sorry to drag up an old thread, but I was googling for some lighting stuff and this came up. Seems useful info, but we have it a little easier in the UK. Volts are 230, which almost halves the current. However, most circuits here are rated at only 13A. Just thought I'd post in case any one else from this side was reading this thread!
David.
 
A note to any wandering pedants: I mean almost half the current when compared with the same power light being used in the US!
 
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