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strong point light sources from sparks


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#1 Andre LeBlanc

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Posted 07 August 2007 - 03:16 AM

Hi all,

I'm trying to brainstorm an effect which involves a character wearing tinfoil, which is sparking due to microwave. I have a method to do the sparking, but my biggest concern at the moment is the strong point light sources that this type of interaction creates. I've been watching several youtube clips of people putting tinfoil in a microwave, and the flash light sources are extremely intense.

Any ideas on how to achieve this strong, yet very specific light source practically? The main issue is that the light flashes from the sparking only affect the character wearing the tinfoil... and only in specific areas of his body during each flash. I've been trying to reasearch a practical method before relying on a 2D composite... but I might be out of my mind.

Any help/suggestions are greatly appreciated.

Edited by Andre LeBlanc, 07 August 2007 - 03:18 AM.

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#2 Jonathan Bowerbank

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Posted 08 August 2007 - 01:39 AM

I'd just go for adding the sparks themselves in post, while practically doing the light flashes on your actor in camera.

Safety first, and I doubt you can do it safely.
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#3 Andre LeBlanc

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Posted 08 August 2007 - 02:36 AM

Hi Jonathan,

Thanks for the reply. Yes, I'll definitely be adding the sparks in post... no question about it. It's the strong source lights caused by the sparking that I've been considering doing practically (at least for the moment). In reality, everywhere a spark occurs, an intense interactive light brightens up the area. I was considering the reverse workflow: I would first try to create the flashes of light on the actor using practical lighting. In post, everywhere there was a flash of light, I would add a spark. The problem is achieving this type of intense, very source specific lighting practically on a moving actor. It just sounds extremely difficult to control... to the point that I'm almost ready to do the lighting in post too. But that will never look as good.

Any ideas?
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#4 Phil Rhodes

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Posted 08 August 2007 - 07:44 AM

Hi,

You might consider looking at magnesium flashbulbs. They're a little out of date now, but you can still get them at least from special effects companies if not some really old-school photography places. It's a plastic bulb with a fairly small amount of magnesium wool inside (like the wire wool you scour pans with, only magnesium rather than steel.) A voltage across the pins heats the wool until it burns. It's a very bright, actinic blue flash, very much like a spark, and they do get hot - hot enough to melt the plastic bulb, so you don't want it in contact with someone's skin or a surface you don't want to damage. I would expect a couple of layers of tinfoil would be more than adequate to protect someone, although of course you should satisfy yourself that the effect is safe. It's certainly a hell of a lot more safe than normal pyrotechnics.

The only ones I've seen from special effects places are quite large, the size of a regular household incandescent lamp, and probably too big. You can strip the flashbulbs out of old cube flash blocks and they're a lot smaller, perhaps 1/4" by 1/2" and concealable.

See:

http://www.meggaflas...0flashbulbs.htm

Phil
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#5 Jonathan Bowerbank

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Posted 08 August 2007 - 01:01 PM

Good recommendation from Phil here. I was gonna say just your basic flash from any type of camera might work too. Or perhaps you could try putting various fresnels, ellipsoidals or par cans on flicker boxes at various angles and see if that works for ya.

:/
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#6 Michael Nash

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Posted 08 August 2007 - 05:08 PM

Seems we had this conversation once before, and the same issue comes to mind: there's a difference between a "flash" and the flickering glow you'd get from visible arcs of electricity.

I'm not sure what the shot has to contain exactly, but I would do it as a composite. Shoot the actor in the tinfoil suit against green screen, surrounded by lightbulbs wired to flicker boxes (preferably the bulbs/wiring don't overlap the actor); and a background plate with similar flicker lighting (units hidden out of frame). Shoot a "clean" background plate (no flicker gag) just for safety, in case the timing of the BG flicker doesn't match the FG well enough. In post composite the two layers, remove the lightbulbs, and add CG sparks and any other color correction that helps embellish the effect.
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#7 Phil Rhodes

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Posted 08 August 2007 - 06:08 PM

You're going to shoot a man in a tinfoil suit - a shiny, multiply-reflective tinfoil suit - against green?

Careful, there appears to be a stampede of fleeing special effects artists coming this way....

Phil
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#8 Michael Nash

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Posted 08 August 2007 - 06:25 PM

You're going to shoot a man in a tinfoil suit - a shiny, multiply-reflective tinfoil suit - against green?

Careful, there appears to be a stampede of fleeing special effects artists coming this way....

Phil


What's worse -- dealing with some mushy green reflections in a comp, or rotoscoping out all the flashbulbs/lightbulbs?

Okay fine; shoot it practically and then a separate background pass, and do a lot of matte work...
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#9 Andre LeBlanc

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Posted 08 August 2007 - 06:42 PM

Being one of those visual effects people myself, I think the green screen could work, but it might be a bit tricky. If the character wasn't wearing the tinfoil suit, then I think it could work very well. It's one of those things I'll want to test both ways before we actually do the shot. But I have a lot of experience on the comp end of things, so we should be able to figure that part out.

In general, it sounds like there's two schools of thought: 1) attach some conceilable flash bulbs to the actor (taking care that they won't burn), or 2) have some pars/flashbulbs either off frame, or away from the actor's field of motion, removing them in post if necessary.

Speaking of flickering lights, has anyone had experience with the Dataflash AF 1000 lights? Might be overkill for this type of effect, but someone had pointed them out to me as possibility for doing the flashing lights.

Edited by Andre LeBlanc, 08 August 2007 - 06:43 PM.

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#10 Michael Nash

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Posted 08 August 2007 - 06:53 PM

Dataflashes are pretty cool, and can be used for a huge variety of effects (and you can choose the number of heads you want to use as well). But keep in mind they are strobes, not "flicker" gags, so you're limited to quick flashes in different speeds and patterns. The effect is full on/full off; no visible warm up or decay. I would think that for an organic spark or electricity effect you'd want something other than a strobe.
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#11 John Sprung

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Posted 09 August 2007 - 02:33 PM

In this case, you'd want to shoot with only the minimum amount of green screen you absolutely need. It'll be far easier to garbage matte the edges of a small green screen than to deal with green reflections in the aluminum from parts of a green screen that are out of frame.



-- J.S.
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