What's the best way to light fog to be opaque?

LesWilson

Well-Known Member
Our venue has a cutout in the ceiling over the apron for an electric. Between it and the HVAC, there's a chimney effect that makes it impossible to do ground fog despite our best efforts in the past. Our fog quickly disperses and becomes haze for a minute and is then gone. Anymore, we design anything with fog to leverage this instead of trying to fight it.

I want to try and get a blind going for the Beauty and the Beast Act II transformation. To cover the body double switch, I want maximum opaque fog but after the prince is in place, maximum shadow through the fog. I think this leverages our fast dispersion environment.

Am I correct that for maximum opaqueness, I should light it from the audience side? Then for maximum shadow effect on the prince emerging from the fog, switch to a single 1K fresnel to backlight the prince when he stands up. I would light the audience side from floor pars rather than ceiling electrics since the body switch is done via trap door and audience sightlines are all low (we don't have stadium seating).

Any thoughts, corrections or suggestions?
 
You've got the right idea. Light from the front for opaqueness, then from behind hitting the actor for the shadow. You might want to aim the PARs at a bit of an angle as opposed to just straight in so any light that doesn't get stopped by the fog will pass to the sides of the actor.
 
You've got the right idea. Light from the front for opaqueness, then from behind hitting the actor for the shadow. You might want to aim the PARs at a bit of an angle as opposed to just straight in so any light that doesn't get stopped by the fog will pass to the sides of the actor.

Just a followup to say this worked well to create a blocking plume of smoke along with positioning the machine at an angle and using a baffle.
 

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If you are motivated enough -- and have enough bodies -- you can run your auditorium a couple degrees cooler than you usually would, and put a cue in to turn off the HVAC 1 minutes before your fog effect fires, and then turn it back on 5 minutes later (or however longer, as long as it's not The Entire Act).
 
@Jay Ashworth : Exactly what we did. Turning off AC is a cue in our script and helps the fog hang a little. However we have to get it back on immediately afterward to keep it from covering the audience (we have flat seating). That blue gelled Source Four Par really did the job of turning the fog opaque.
 
@Jay Ashworth : Exactly what we did. Turning off AC is a cue in our script and helps the fog hang a little. However we have to get it back on immediately afterward to keep it from covering the audience (we have flat seating). That blue gelled Source Four Par really did the job of turning the fog opaque.
You might also want to run the machine output through a bed of dry ice. It really makes it behave better! Outright dry-ice foggers fell out of favor many years ago because of the logistics, but I always loved the way they fogged. Much more realistic. After their demise, a few companies marketed basket products to make a standard fogger look more like fog by passing their output through dry ice.
 

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