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View Full Version : source video of lightning to trigger opacity of white solid?



stip
04-30-2014, 07:09 AM
Hey,

I'll have several stock footages of lightnings projected on a wall/BG in a studio. I want to have a second beamer pointing on 2 talents in front of the background projection and have light flashing on them acccording to the lightning flashes of the background video.

Talents should be in the dark except when the lightnings flash.

There should be a way in AE to trigger a white solids' opacity from the brightness of the source video, but how do I get both projectors to play the files in sync?

Maybe any other idea how to get a bright 'lightning' light on the subjects in sync to the flashes of the background stock footage projection?

THX!
stip

Finn Yarbrough
04-30-2014, 12:37 PM
If you can get hold of a stills photographer, they will have strobe sets that will trigger many bright lights simultaneously. This seems the simplest to me.

stip
05-13-2014, 06:37 AM
If you can get hold of a stills photographer, they will have strobe sets that will trigger many bright lights simultaneously. This seems the simplest to me.

I'm afraid those will be too fast for cmos sensors.

Here's how to control brightness of layer A from source video B (same should work to trigger opacity)

http://www.videocopilot.net/forum/viewtopic.php?f=5&t=58834&p=230136&hilit=opacity+from+brightness#p230136

Right now I'm thinking of making a 3840 x 1080 video with the source video on the left half and the white layer video on the right half and send out the left half (1920x1080) to one projector for the background and the right half to one or two other projectors for keylight onto the subjects.

Can this be done (determine only an area from a video to be shown by the projector)?

Michael Carter
05-14-2014, 11:45 AM
There may be a way to do it using sound as a trigger... if you add some blips or tone where the lightning flashes and run the audio out to something that would trigger a strobe or a bright light.

Couldn't tell you what sort of gear would do that, but it likely exists - just thinking outside the box... there's lots of DJ lighting gear that is triggered by audio, likely some xenon strobes that are cheap.

legrevedotcom
10-20-2014, 12:26 PM
You can get led par cans that respond to sound.