help with a chromakey flash effect

Jeff Waters wrote on 8/22/2007, 6:22 PM

Hi Gang,

I've just stepped into the world of greenscreen. Great stuff. I'm planning a new project (fitness training video) that will be shot in a well lit gym. Once the shoot is done, I will record the trainer against a green screen delivery extra little tips for each drill.

I plan to edit this thusly: As the action is moving along in the gym, I will freeze and darken the screen. Then I want the trainer (keyed out to just the trainer) to appear on the screen with a nugget of wisdom to watch for when the screen unfreezes.

I'm looking for an easy way to make the trainer flash pure white siloutte in rapid fire as a bit of a little transition. Really appreciate any ideas or tips you can shoot at me!

Thanks,
Jeff

Comments

richard-courtney wrote on 8/22/2007, 7:20 PM

I am not sure what you are asking for.

Is the gym video something you can prerecord and play on a monitor just off
camera next to the green screen? This will give the trainer cues when to
start and stop.

There is an option in the Sony Chroma keyer FX to show mask only.
Turn this on and render your green screen segment as an uncompressed AVI.
Use this video clip later to key. Uncompressed is needed to retain the alpha
channel.

Generate a third video clip using keyframes.
Place a white background using media generator's solid color on a track
above the green screen track. Set keyframes adjusting the opacity of the white
track. You WILL see the green background in this rendered clip.
The key AVI clip with Alpha made earlier controls what will be seen over the
gym including flash of the instructor when composited.

Now you should have enough to composite.
You can add a sound effect swish to add to the flash transition.

Jeff Waters wrote on 8/23/2007, 4:04 AM

Thanks,
I think I'm begging to see the issue here. It seems that when you apply FX after the Chromkey FX, it still applies that fx to the whole screen, not just the object that has been keyed out.

So, if you have a good key with alpha over most of the screen, applying somehting like "black & white" will over-ride the alpha transparent sections of the screen, too.

How can you apply FX to just the "person" who is standing out on the greenscreen?

richard-courtney wrote on 8/23/2007, 6:44 AM

Keep in mind you can use the key footage to control what is keyed in and out.

I did a soccer opening with a player on a green screen.

Actor is replaced with black/white by as an event FX not a track FX,
and the background key is not changed..

See previous post about saving alpha.
Top track pair displays actor using a mask file.