Shooting a white background instead of green screen?

[Todd Terry]

It depends on what you are trying to do and what you want the end result to look like.

If you want your talent in a white limbo background, then shooting over white is ok, then use a luma key to clean up any dirty parts.

But if you want to put your talent in a different environment (an office, a meadow, or just over some background plate), then I would never use white as a background.

Blue or green are used as key background colors because they are most opposite of skin tones. White, on the other hand, contains all colors…. 100% of blue, red, and green. If you try to chromakey it, you’ll get a very dirty key indeed. At least chromatically your talent in the gray suit is exactly the same color as your background… even amounts of RGB… just not as much of it. Your only choice would be to luma key it, and it’s still likely going to look pretty ragged.

If you have to go the lumakey route, your better bet would probably be putting them in a pure black environment rather than white… which would allow you to light your talent in a more refined way, independent from a glaring white background that might give you a fair bit of unwanted spill.

I do luma keys on occasion when appropriate… but putting human talent in another environment is definitely a case for greenscreen or bluescreen.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com

[Mark Suszko]

What about if he uses a difference key, instead of a luminance key?

[Daniel Weaver]

Thanks for the great replies guys.

I will be compositing it later, but it will not be a photoreal. It is to be a video montage / music video. And it will be mostly blacks and whites, desaturated. But despite that I don’t want any color information to be missing, because I’m after a very high quality video. Why would a pure black environment be better? How would I separate my talent from it? Would I use white clothing? What is a difference key and how can I use it?

So I guess my main issue here is, would I be better off

1. Using a shoddy green screen, that gives a bad, rough key. With not a lot of light available.

2. Use a white screen, and get high quality footage, but sacrifice some of the colour information during the key.

Also, Roto scoping is NOT an option. There is no budget or time for that.

Cheers again

[Todd Terry]

Your best option is neither of those… best is to shoot it on greenscreen or bluescreen WITH a well-lit background.

If that’s not possible, I’m not sure what I would do, but I don’t think I would ever choose a luma key over white.

Shooting on black instead of white would negate any “spill” from the very hot/bright background… usually when chromakeying that means some green reflecting back onto the talent (and it’s still a luma key… just black instead of white, of zero luminance rather than 100%). In this case with a white background, it might mean some very hot highlights on the talent that would also key out. Not good. You also have, in effect, a gigantic very hot all-encompassing soft backlight. You might want that, but you might not. In most cases I would think not. You say you are wanting photorealistic insertions into other environments, therefor for each shot your talent should be shot with lighting as if they were actually on the location… and it’s doubtful that most locations would have a gigantic super-soft and super-bright backlight.

A “difference matte” is where you shoot a scene… and then you have the talent leave that scene and shoot a clean plate without them. Then when applying a difference matte, the only thing that is matted is what is different in the two scenes… which in this case would be the person. Difference mattes work ok, but not great often times. They tend to work best with busy or non-uniform backgrounds, so a pure white background would be just about the most uniform thing there is. You also must have a locked-down camera (so absolutely no camera moves). You also have to remember to take a clean plate without the talent for each setup… although if the background is just pure white you might not have to do that (although I would, just to be safe). I’m not sure it’s a technique I would try in this instance.

Greenscreen wtih good even lighting is the best bet. And again, try to match the lighting on your talent with the lighting in whatever environment you are using as a background plate as closely as possible.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com