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Fading Lighting Setups mid-shot


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#1 Colin Theys

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Posted 23 August 2005 - 11:09 AM

Hi,

I'm DPing a very cool little fairy tale project. The script calls for a very strange sense of time. One of the effects we were planning to use was to fade between different lighting setups during a single shot - ie transition from day to evening. We're students and doing this on a budget. :)

Basically, my question is how serious the color temperature change will be if I jsut go to home depot and build myself a fader board with a few 1k faders so that we can fade between the two setups. I will of course shoot a test of this (even if only on video) before using it, however if anyone has any experience with this it woudl be helpful to know before I build the board. :) I've used faders on a shoot before, but it was black and white.

Thanks,
-Colin Theys
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#2 John Pytlak RIP

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Posted 23 August 2005 - 12:25 PM

Hi,

    I'm DPing a very cool little fairy tale project. The script calls for a very strange sense of time. One of the effects we were planning to use was to fade between different lighting setups during a single shot - ie transition from day to evening. We're students and doing this on a budget. :)

    Basically, my question is how serious the color temperature change will be if I jsut go to home depot and build myself a fader board with a few 1k faders so that we can fade between the two setups. I will of course shoot a test of this (even if only on video) before using it, however if anyone has any experience with this it woudl be helpful to know before I build the board. :) I've used faders on a shoot before, but it was black and white.

Thanks,
-Colin Theys

<{POST_SNAPBACK}>


Just a note of caution that the typical low cost Triac or "SCR" dimmers used on household lighting actually "chop" the sinusoidal waveform voltage feeding the lamp, so you can get a bit of flicker or buzzing, especially with lamps having thinner filaments. Resistive or variac type dimmers don't adversely affect the waveform, and are less prone to flicker issues.
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#3 Tim Tyler

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Posted 23 August 2005 - 01:41 PM

I recommend you call a theater supply company and price out a rental for gear that will let you operate your lights from a board. I don't think it will be that expensive, and it will make your life easier. The stuff you rent will be able to handle larger lamps, while Home Depot dimmers are usually limited to under 500watts, and sometimes under 300w.

I use hardware store dimmers all the time for really small inkies and practicals, but I'd never put a 1k on one.
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#4 Adam Frisch FSF

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Posted 25 August 2005 - 09:22 AM

You can also use old-school venetian blind light vanes to stick in front of the source - they dim without changing the color temp. Don't know how easy they are to get, though. :(
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#5 Colin Theys

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Posted 25 August 2005 - 12:41 PM

Thanks for the suggestions / tips. It had never occurred to me that the triacs would cause the lights to flicker. Buzz I can live with because we're probably shooting silent or close to it most of the time, but flicker is not so cool to say the least. I've seen home depot dimmers used on arri openface 650s and 300s, so maybe I can get away with lighting that shot completly with 650s and under and then gang together a few dimmers to ensure that the transition is smooth? I'll do some tests and see what I can get and if it doesn't work, I know a bunch of people in theater lighting professionally. Perhaps time to call in a favor. :) or better yet... I could raid the theater department.... hrmm... ;)

Thanks,
-Colin
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#6 John Pytlak RIP

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Posted 25 August 2005 - 01:27 PM

Thanks for the suggestions / tips.  It had never occurred to me that the triacs would cause the lights to flicker. Buzz I can live with because we're probably shooting silent or close to it most of the time, but flicker is not so cool to say the least. I've seen home depot dimmers used on arri openface 650s and 300s, so maybe I can get away with lighting that shot completly with 650s and under and then gang together a few dimmers to ensure that the transition is smooth? I'll do some tests and see what I can get and if it doesn't work, I know a bunch of people in theater lighting professionally. Perhaps time to call in a favor. :)  or better yet... I could raid the theater department.... hrmm... ;)

Thanks,
-Colin

<{POST_SNAPBACK}>


Not sure you can "gang" SCR dimmers to increase power capacity. I have seen some larger units that can handle 1000 watt lamps. But when you dim using a SCR dimmer, the pure sine wave of the incoming power is "chopped" into a "spikey" waveform at the same frequency. So a lamp with a thinner filament will actually flicker more than if fed with a pure sine-wave AC.
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#7 Colin Theys

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Posted 25 August 2005 - 03:20 PM

Not sure you can "gang" SCR dimmers to increase power capacity.  I have seen some larger units that can handle 1000 watt lamps.  But when you dim using a SCR dimmer, the pure sine wave of the incoming power is "chopped" into a "spikey" waveform at the same frequency.  So a lamp with a thinner filament will actually flicker more than if fed with a pure sine-wave AC.

<{POST_SNAPBACK}>



Sorry, I guess I didn't make that clear. i didn't mean to incrase capacity. I meant ganging them together so that you could easily dim one light while simultaneously 'undimming' another. :)

Reading about all this stuff, I stumbled across this pretty decent page about how these dimmers work: http://home.howstuff...mer-switch1.htm

Thanks,
-Colin

PS. I could see some 'interesting' situations developing from attempting to increase capacity by using multiple dimmers. hehe.
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#8 Jeremy

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Posted 25 August 2005 - 03:21 PM

You can go out to a lighting wholesale store (almost every medium to large sized town has one) and buy a 1k dimmer that you can wire to an extension cord. I've built several of them and use them on 1ks and 650s all the time. The color variation is minimal (as you fade down it warms slightly), and I think if it was noticeable, it would fit just fine for a fairy tale piece on a budget.
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