size for greenscreen format...

#1

Hi all…making a student film and I’m considering using a greenscreen.
I’ll be using a combo of Max and photoshop for the background matte to be projected onto the screen.
My question is…how large and what format (dimensions and resolution) should it be?
It’ll most likely be a closeup and maybe a medium camera shot…no wides.
Should I consider HDTV like 1920 x 1080 or one of the other formats ( ntsc dv, 35mm academy…).
The film will be shot in digital video.
I’ve never done greenscreen (although we’ll cover it I’m sure in class) but any other considerations regarding output to greenscreen would be great.
We’ll probably only cover greenscreen and editing but not mattes or how to utilize my 3d app with greenscreen.
thx in advance…
Joe

#2

The film will be shot in digital video.

You answered your question yourself. Choose the videos resolution for your matte output.

#3

you don’t project onto green screen
you shoot your actors with the screen behind them(soundslike your using digital video)
you’ll ened to use aftereffects or shake or nuke to extract the green from your video (not a 3d app)
the 3d will be used to make your background in Max or whatever and render out digital viewo res (720x486 .9 pixel aspect ratio) and then composite that render behind your acter with the matte pulled.

#4

If you can help it, DO NOT shoot the greenscreen on DV. Use HDV if you can.

DV does not store the color channels of the image (RGB) with much data, so if you look at your green channel, it will be crappy. And this is important because keyers use the color information.

There are quite a few workarounds out there for how to treat DV footage to get better keys from it, but you can avoid all that by just shooting on something else.

For example, here’s an image from Stu Maschwitz’s book “The DV Rebel’s Guide”

the images on the left show the footage, and below it the blue channel. See how crappy it looks? That means the key is going to be crappy, too. The images on the right side show how the color channels are altered after running his DV Artifact Remover. Much better, but if you can avoid it, you should. HD won’t do this.

The workaround involves changing the color space of the footage and blurring only certain channels, then changing it back. Like this…

http://www.aenhancers.com/viewtopic.php?f=4&t=40

That’s an example for After Effects, but if you read what he’s doing, you should be able to duplicate it in whatever compositing program you want.

#5

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