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Compositing and On-Set Fog?

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Max JacksonCompositing and On-Set Fog?
by on Jun 16, 2011 at 4:42:04 pm

Hi CC,

I'm doing a shoot in the next couple days. Now, one thing in my production notes that really has me hesitant is using a fog machine. I planned on using it, but I'm really concerned of it's using in overlapping greenscreen foreground elements with the BG plate, both with fog.

Is that a screen job take unto itself? Just dust/fog over a greenscren BG? That would be my first instinct, but what if I'm trying to capture the fog from window light in a foreground or BG shot? I wouldn't imagine a simple blend mode to do the job would it? I imagine modes would have no consideration for windows projection.

How do people go about handling something like that?

As always I'm thankful for any feedback on this issue.


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Mark SuszkoRe: Compositing and On-Set Fog?
by on Jun 16, 2011 at 6:39:29 pm

Ultimatte has been touting that they can key water glasses, hair, smoke and fog for years. My take is that it boils down to do you have the right gear, lighting and software to pull it off. And if this is important to you, you'll run test shots before the shoot day, to confirm it. I have had to compoite smoke and fog into a scene after the shoot and it is very hard to make it look realistic, but much easier if you have even just a few wisps of the real thing on-set.

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Max JacksonRe: Compositing and On-Set Fog?
by on Jun 16, 2011 at 6:46:56 pm

Yeah, as I gather doing fog in the box is really just not the same as on set.

I was thinking about doing a green screen shot of just the fog, and then composite it.

This shot is really challenging. I'm also guessing that adding fog would help create a lot of noise in the image as well, right?

It'd be great to have at least just a little fog as the set has a street light pouring through a basement window. Having a touch of thickness would be great. However, I don't want to blow the entire shoot because of it, you know?

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Joseph W. BourkeRe: Compositing and On-Set Fog?
by on Jun 17, 2011 at 1:27:23 pm

Why not hedge your bet and shoot it both ways? Once you're set up and lit, just shoot a no fog version, maybe a light fog version, and a heavy fog version?

Of course, if this shoot is comprised of multiple smaller setups, you may not have that luxury, but I'd certainly push for it. I shouldn't double the shoot time, and you'll sleep easier.

Joe Bourke
Owner/Creative Director
Bourke Media

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Max JacksonRe: Compositing and On-Set Fog?
by on Jun 17, 2011 at 3:00:24 pm

Hi Joe,

Yeah, that's the thing. My shoot comprises of one small set in ambitious schedule. I just don't think I have enough time really to make fog happen.

I have real "spotlights" coming through the window. That will have to do for this one before it's in the can I'm afraid.

Thanks for the suggestion though! :)

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Mark SuszkoRe: Compositing and On-Set Fog?
by on Jun 17, 2011 at 5:30:32 pm

This stuff looks like a joke, but it really worked well for me on a project.

Nontoxic, won't trip smoke alarms or set off asthmatics, leaves no messy residue, works at any temperature, no warm-up time like with fluid fog machines.. Has a respectable "hang time" in a room where there are no drafts. How I used it was in a studio to get a dramatic beam of light from an old movie projector.

Also, in a safety training video, I sent puffs of this under the door, backlit with flickering red and orange gels, to simulate a fire on the back side of the door. Later in that same video, A few puffs of this near the lens sold the visual idea of smoke starting to get into a room, and then a layer of more smoke, shot against limbo black, was keyed in during post. The layering of practical and animated effects was better than either one alone. In that same video, we also did an earthquake scene, where I shook the camera, had a stagehand drop chunks of lightweight ceiling panels down from above the lens, and I added puffs of this FX spray to simulate dust falling down. It really helped and was very cheap to do.

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Max JacksonRe: Compositing and On-Set Fog?
by on Jun 17, 2011 at 7:55:01 pm

That's awesome! I'll let me crew know for posterity.

Thanks Mark!

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Walter SoykaRe: Compositing and On-Set Fog?
by on Jun 19, 2011 at 9:05:16 pm

If you composite fog after the fact, you may need to use several layers of it to preserve a sense of depth with other other composited elements.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events

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Stephen SmithRe: Compositing and On-Set Fog?
by on Jun 24, 2011 at 8:49:25 pm

Take a look the the Compositors Toolikts:

Stephen Smith
Utah Video Productions

Check out my Motion Training DVD

Check out my Motion Tutorials

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