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Croma key shoot


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#1 Chakresh

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Posted 22 August 2007 - 12:05 PM

Im doing Chroma shoot for a Corporate Video, with two characters in every frame with some walking around & stuff. My queries are as follows:-
1) hw to lit up the background & the foreground without the spill of light on each other & what lights are recommended?
2) wat cameras are good for better result?
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#2 David Auner aac

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Posted 22 August 2007 - 12:15 PM

Im doing Chroma shoot for a Corporate Video, with two characters in every frame with some walking around & stuff. My queries are as follows:-
1) hw to lit up the background & the foreground without the spill of light on each other & what lights are recommended?
2) wat cameras are good for better result?


Hi & welcome to the boards. Please change your user name to your first & last name. Thanks.

Concerning your questions:

1. The most important thing is to have enough distance between the green/blue screen and the talent. This becomes harder when you have a green floor as well. Try to avoid that if possible.
If you're using tungsten lights on blue screen you can put some CTB gels on the lights to shift your colour temperature towards blue.
Be sure the keep your key lights off the screen by using barn doors and flags. Also be sure to have some kind of back light to separate your talent from the screen. Spill is usually most visible on the shoulders and in the actors hair. That's about all I can think of right now.

2. Use the camera that captures the most colour information possible. I.e. prefer DVCPRO50 or D-9 or any other 4:2:2 video format over MiniDV or Betacam SP. Chroma keying can be done with MiniDV or DVCAM, but it won't look all that good. You'll get color artifact on the seams. Be sure to use some kind of spill suppression if possible. And have your talent avoid clothing in any shade of colour you're keying with. If that's not possible, you'll spend quite some time cleaning up your mattes.

HTH, Dave
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#3 John Sprung

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Posted 22 August 2007 - 12:32 PM

... or any other 4:2:2 video format over MiniDV or Betacam SP.

Better yet, go 4:4:4. Chroma keying uses color data to decide where the matte line goes, and 4:4:4 has twice the resolution there of 4:2:2. For that reason, some compositors will pull a luminance key instead if you give them 4:2:2. That often works on green screen because most systems have luminance equations something like Y = 0.7G + 0.2R + 0.1B.



-- J.S.
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#4 Chakresh

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Posted 23 August 2007 - 09:16 AM

hi there,
Thanks fr ur quick & precious infrmation about both my queries... :)
Apart frm this i've some more doubts:
1) is it necessary to hire a video mixer on set, to match the outcome with the 3D animation(as my final product is, 3D in background & live action in front)?
2) what is the ideal F stop to shoot!!!
Once again thanks a lot...












Hi & welcome to the boards. Please change your user name to your first & last name. Thanks.

Concerning your questions:

1. The most important thing is to have enough distance between the green/blue screen and the talent. This becomes harder when you have a green floor as well. Try to avoid that if possible.
If you're using tungsten lights on blue screen you can put some CTB gels on the lights to shift your colour temperature towards blue.
Be sure the keep your key lights off the screen by using barn doors and flags. Also be sure to have some kind of back light to separate your talent from the screen. Spill is usually most visible on the shoulders and in the actors hair. That's about all I can think of right now.

2. Use the camera that captures the most colour information possible. I.e. prefer DVCPRO50 or D-9 or any other 4:2:2 video format over MiniDV or Betacam SP. Chroma keying can be done with MiniDV or DVCAM, but it won't look all that good. You'll get color artifact on the seams. Be sure to use some kind of spill suppression if possible. And have your talent avoid clothing in any shade of colour you're keying with. If that's not possible, you'll spend quite some time cleaning up your mattes.

HTH, Dave


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Technodolly

The Slider

Aerial Filmworks

Paralinx LLC

Gamma Ray Digital Inc

Willys Widgets

Ritter Battery

CineTape

Opal

CineLab

Tai Audio

FJS International, LLC

Abel Cine

Glidecam

rebotnix Technologies

Metropolis Post

Broadcast Solutions Inc

Visual Products

Rig Wheels Passport