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yearnandlearn
chromakeying head to toe
on Oct 3, 2007 at 1:14:43 pm

When attempting to chroma key a person from head to toe (20x 30 greenscreen)how do you eliminate the floor shadows? I'm using two light kits. No lighting grid. Two back lights, two lights for the chroma key wall, two soft lights for the talent. The talent is to walk into the frame from the left side to his mark.Will this key properly? Also, what color gel should I use for the backlight? The talent will be wearing a dark colored suit. (I hope.)
Thanx,
yearnandlearn


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HowDoYouDoThat
Re: chromakeying head to toe
on Oct 3, 2007 at 4:24:39 pm

What wattage and what color temperature? How tall is the ceiling and how much depth in the room where your setting up? And do you have a waveform?

Do you have access to HMI's?


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Leo Ticheli
Re: chromakeying head to toe
on Oct 3, 2007 at 4:33:46 pm

There is nothing really different about doing a head to toe key, it's just more difficult to achieve good results.

All the usual guides apply:

1. Light the screen evenly! If you don't have the lights to do it, you can't be expected to produce good results. You can overcome this in post by doing separate parts, but don't expect love from the compositor!

Lighting evenly is much more difficult with the cove and floor reflecting the light much differently. Succeeding with just two lights is doubtful.

2. Never put colored gel on the back lights; this will produce a colored edge that looks unnatural. Some still recommend a yellow gel to counteract the green, but I've found it just introduces more problems.

3. The larger your softlight sources on the key lights, the less shadow they will cast on the green screen. I use a 4'x6' Chimera in front of a 5k and as large as possible, say 12'x12' for head to toe.

4. I'm sure you'll be trying to have as much distance as possible for the subject from the back wall, but the floor is right there bouncing green spill all over the subject. I know of no solution for this, it's all down to the compositor's skill.

Hope this helps.

Good shooting and best regards,

Leo


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Bob Woodhead
Re: chromakeying head to toe
on Oct 4, 2007 at 1:18:42 am

Echo all of Leo's suggestions, and add that you don't need to eliminate shadows on the greenscreen (talent shadows, that is) - your compositor can use these as keyed shadows, or, they're usually easy just to eliminate. More importantly, don't let your talent wear anything shiny!!! Highly polished shoes... FUGGITABOUTIT. Big shiny reflective jewelry... nooooo. I've done greenscreens with lace, smoke, wispy hair... no headaches.... but then the talent comes in wearing shiny black vinyl, and it reflects green everywhere! Wot a headache.
With moving talent you'll probably need more lights (as suggested) to keep things even as talent moves. *not* hot lighting... EVEN lighting.

"Constituo, ergo sum"

Bob Woodhead / Atlanta
http://www.CoolNewMedia.net
Quantel-Avid-FCP-3D-Crayola


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