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Old April 11th, 2007, 07:14 AM   #1
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new lights or dimmers?

Hi,

I use a Mole Richardson biax-4 for a key light and have recently been given two fixtures with 650 W lamps. They're great but 650 is a lot of light. Is it better to get smaller lights or dimmers? If dimmers, which ones?

Thanks,

Ty Ford
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Old April 11th, 2007, 07:26 AM   #2
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I would get dimmers as you can turn the big lights down, but you can't turn a small light up. The controllers range from very expensive to cheap.

I have three router speed controls, bought from Harbor Freight. I got them on sale for less than $20.00. The are 1500 watt and have full and variable controls. They work excellent! No problems at all. You have to look hard for them as they are sold out just about as fast as they come into stock. I think yo could order them on-line but the price will be about $29.00 I think. A bargain either way.

Mike
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Old April 11th, 2007, 10:47 AM   #3
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Only problem with dimmers is you change the colour temperature. You could buy some scrims (metal nets) which will reduce the light output. They're pretty standard pieces of kit and you can get different grades. Another alternative are ND gels.
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Old April 11th, 2007, 11:07 AM   #4
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Dimmer RF

Ty,
Not sure about the Harborfreight dimmers, but many cheap diy/hardware store units will create RF problems for audio.
Test,test, test etc.


chris li/bethesda DP
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Old April 11th, 2007, 11:37 AM   #5
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Harbor Freight dimmers

Hi:

Noticed the thread and thought that I would add my two cents.

I have a handful of the Harbor Freight Dimmers, recently on sale for $9.99, and have not found them to introduce any RF interference at all. They work great with the Arri system and for the price, cannot be beat. The only caveat is the fact that they do not have a calibrated dial.
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Old April 11th, 2007, 01:38 PM   #6
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I'd vote for dimmers too. While the color shift when dimming tungsten units is real, it doesn't become much of an issue until you are down below something like 50% on the dimmer. With a few scrims in your kit, you can usually get what you need without much change in color temp. Dimmers are fast and let you dial in exactly what you need.

Almost any dimmer will work for 650W units. Even do-it-yourself Home Depot dimmers can handle that, although the possibility of RF noise does exist. I carry a pair of AC in-line Quick Dimmers from Bill McIntire's "Magic Gadgets" website. They'll handle 2K watts with ease, are small, light weight, absolutely quiet, and built like a tank. Their only downside is cost.
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Old April 11th, 2007, 02:05 PM   #7
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There was a recent very informative conversation on the B-Roll forum about dimmers. Check it out.

http://b-roll.net/forum/showthread.p...hlight=dimmers


Nino

www.EFPlighting.com
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Old April 13th, 2007, 12:12 AM   #8
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yeah, I think lights start changing color temp around 50%....at least that's what my teacher told us in basic tv. I don't know how a dimmer could add interfernce either since a dimmer adds more resistance. On old cars there where radio problems because the spark plugs had next to no resistance and you could hear the plugs firing through speakers. When cars moved to plug wires with resisatnce in them the unwanted noise in the speakers quit. (the plugs originally used like +8000 volts).
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Old April 13th, 2007, 01:54 AM   #9
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Ty,

My "order of priority" for lowering the amount of light hitting any subject is as follows.

Use a scrim
Move the light farther away
Use N/D gel
Use a dimmer

The scrim is simple, quick, inflamable, and doesn't screw ANYTHING else up when you use it. Plus a one stop scrim will reliably lower your light one stop. No more or less. It just knocks back the light, PERIOD.

Moving the light farther away is similarly without negatives, UNLESS, of course, you can't move the light - which happens.

ND is similarly pretty effective, but it takes a bit more time to rig and on a hot light like a 1K Tota or other open face insturment, even quality theatrical gel has a melting point.

The dimmer is LAST on my list because over the years the use of dimmers has screwed me up more than any other solution. Audio effects, color shift, or just some knucklehead kicks the dimmer and no matter HOW I try to re-adjust it to where it was on the first 3 takes, the damn shots NEVER match in post.

I'm not saying they aren't nice to have around and they're often useful. But just know that when you use them, you're putting one more "variable" in play on your set.

Your mileage may vary. Good luck.
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Old April 13th, 2007, 05:11 AM   #10
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Quote:
Originally Posted by Eric Stemen View Post
I don't know how a dimmer could add interfernce either since a dimmer adds more resistance.
Silicon control rectifiers in dimmers generate noise as a byproduct of the way they rip portions of the AC sine wave in order to lower the energy (dim) the light.

I hear that noise when cheap (residential) Leviton dimmers are used.

Regards,

Ty Ford
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Old April 13th, 2007, 07:46 AM   #11
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Quote:
Originally Posted by Ty Ford View Post
Silicon control rectifiers in dimmers generate noise as a byproduct of the way they rip portions of the AC sine wave in order to lower the energy (dim) the light.

I hear that noise when cheap (residential) Leviton dimmers are used.
Quite right, Ty. The best dimmer (although pricey), is the VARIAC. It is a variable AC transformer and can be bought in many size/ratings. The other downside is that these are kind of heavy.

http://www.variac.com/staco_Variable...former_Map.htm

-gb-
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Old April 13th, 2007, 07:54 AM   #12
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Another option would be to replace the 650w lamp with a lamp of similar design, but less wattage.
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Old April 13th, 2007, 08:15 AM   #13
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Thanks for that David,

I have already come down to 650 from 1 kW (boy is that bright!).

Don't know if they make, what, maybe 250-300 watt bulbs for these fixtures.


Regards,

Ty
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Old April 13th, 2007, 03:54 PM   #14
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Thanks for the info Ty Ford.
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Old April 16th, 2007, 07:45 PM   #15
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Harbour Freight

I hear the whining when I dim a bulb with the cheapo router speed control. My longer tube type bulbs make more noise than the smaller peanut type bulbs. They might be ok with the speed control, but I can hear some noise up close, for reasons mentioned before.

For a more technical pov and possible fix from another web site "The inductor slows the rise time of the AC wave when it turns on. In turn this provides two functions: 1) it reduces EMI (electromagnetic interference) created by the sudden rise in voltage in the wires, and 2) stops light bulb filaments from rattling. When you turn the typical home dimmer down low, you can hear a buzz in the light fixture - that is the filaments rattling as the voltage is suddenly applied to the bulb.

I'll dig up my digital electronics book and maybe ask my former instructor if there is a cheap fix.
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