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Old August 18th, 2007, 01:49 PM   #1
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In camera lighting effect

Hi guys,

I'm a director with basic lighting experience - I can 3 point light a talking head interview in my day job (news broadcast) but beyond that I rely on talented DP's working their magic with my concepts.

But I've got a concept for a music video shooting in a few months that I'd really appreciate some input on. (budget just 2000 UK)

Basically, we want to have a good number of practicals in the frame - maybe 5, maybe as many as 50. These will be regular light bulbs - probably quite low wattage. The set will then be lit to appear as if these practicals are illuminating it.

Here's the trick. I want to get the practicals and the 'real' blondes / reds / hmi's etc to dim down / dim back up in unison in time with distintive beats at certain stages of the song. So that the entire set gets darker and then lighter as we play with dimming the practicals.

At the moment our best idea is to wire the practicals and the 'real' lights into a programmable theatre lighting board. Which means we need to bring someone with experience of theatre lighting on board. I'm also aware of problems with simple things like the length of cable from the various practicals - ie: the bulbs on shorter cables may dip fractionally before the ones on longer cable runs.

I'd really appreciate if anybody has any outline thoughts as to whether we are going down the correct route. And any alternatives or observations you may have.

Many thanks to this board as ever,
Marco
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Old August 18th, 2007, 05:01 PM   #2
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If you're using HMI,

1). trying to dim it via DMX will be quite a trick since most of them don't have dmx inputs.

2). you can't dim them by lowering their line voltage input like tungsten. That'll just potentially damage their ballasts. You'll be buying a bunch of non-working HMI's from your rental place if you damage them perhaps...

3). practically no hmi dims past 50% because thats just the nature of the metal halide family. You can't dim it past 50% without losing ignition. If they claim to dim past 50%, there's usually some other trick involved.

4). there may be a delay even if you can dim it via dmx--thus not in time with your song.

Otherwise, I'd use all tungsten, they can all be dimmed via dmx dimmer packs through a board and will all respond much quicker than any ballast-oriented like flo or hmi lighting would. Hope this helps.
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Old August 18th, 2007, 07:32 PM   #3
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Also you wouldn't really want to be trying to match HMI to incandescent bulbs when tungsten units will match better and be easier to work with (and cheaper to rent)!

1/4 CTO on the incandescent fixtures will match the practicals perfectly. If you want to keep it simple, you can just gang each set of practicals along with the appropriate tungsten units together into a squeezer (aka variac) of the appropriate wattage. One person will be able to control two variacs simultaneously, so if you want a lot of separate cues you'll need a bunch of people on it. Obviously clunkier than a DMX system but possibly easier for you guys to use and again, cheaper.
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Old August 19th, 2007, 07:53 AM   #4
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"I'm also aware of problems with simple things like the length of cable from the various practicals - ie: the bulbs on shorter cables may dip fractionally before the ones on longer cable runs."

Electricity travels at the speed of light. Longer cables only cause problems if they are insufficient to handle the amperage as they will heat up. Cable length effecting timing of circuits is only really relevant in supercomputers.

It sounds like this situation might be better handled in post with digital filtration. I can't remember the name of the fade, but I have seen post work done that looks rather similar to a lighting fade. This would give you more precision and probably cost a lot less. Of course, this is assuming you want the whole scene to fade simultaneously.

"So that the entire set gets darker and then lighter..."
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Old August 27th, 2007, 03:12 AM   #5
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Thanks

Thanks very much guys - that's all incredibly useful. As ever dvinfo is helpful and encouraging.

I'll keep exploring the options.
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