WoMP: Greener Screen

This is the latest of my not-quite-safe-for-work-but-ultimately-harmless camera/filmmaking/review show thing (I need to work on that pitch).

We focus on greenscreen, and in particular finding just the right shade of paint.  It actually ended up being immensely challenging.

Some background:  Rosco is the de facto standard in greenscreen paint, but even they can’t seem to decide what’s right.  They make three vastly different colors, all kinda billed to do the same thing.  Hollywood types aren’t quite sure which to choose when and why.  It’s because it’s actually a fairly complicated issue and there is no one right answer.  Anyone that tells you so is trying to sell you something.   There are a couple problems that I discovered in my travels to many a paint store this month.

Firstly, not all chroma-key software is made to use the same algorithms to extract the key.  They’re all similar, but tweaked in their own special ways.  So whereas one software might really need a saturated color, regardless of an imperfect hue, another might prefer the muted-but-accurate color.  Secondly:  Paint is imperfect.  It’s a real world substance made from real chemicals and not some theoretical physics-of-light equation.  It’s not like someone can press a magical button and make a dye that only reflects exactly one wavelength of light; that substance simply doesn’t exist.  Anything we do is just a best try.  Thirdly:  Greenscreen work is often a trade-off:  amazing key vs. excessive spill; super vivid color paint vs. accurate color; etc.

What I’m saying here is that after all this testing it actually makes MORE sense to me that Rosco can’t decide on a paint.  If I had to choose one paint on the planet to use, and price was no object, I’d probably use Rosco’s Ultimatte, AND then I’d be crazy aggressive about blocking off un-used portions of the screen during a shoot to reduce spill, cause it’s a vivid paint, at times it would be too much so.

In a more practical world (where price and spill are a concern), I recommend the stuff I got mixed from Sherwin Williams.  The reasons we ended up going with that blend:

  • One of the flatter finishes I could find; although I’d like an even flatter finish, but we couldn’t find one in an interior paint base (and exterior paints may emit toxic chemicals for years).
  • Exposure: One of my complaints with the more vivid ‘pro’ paints is that under “average” lighting, that is a shot that is properly incident metered, they are very bright, pushing the top end of my exposure.  I’d rather have something in the ballpark of the average things I’m shooting, lest I run into problems if I have to open up a bunch to expose a subject brighter.  This is the big difference between Rosco’s “digi” vs their “chroma”.  Their “chroma” basically exposes right around middle grey, as does my blend.
  • Saturation:  Good separation between green and the other channels is critical.
  • Hue:  This paint is very even on red and blue, and if anything is actually skewing a bit away from the red.  The reason I like this, is because I call it “playing it safe with the yellows”.  When shooting on greenscreen the biggest problem I run into is light hair and/or yellow in the wardrobe (cyan hair is far less common).  So I definitely don’t want a green that skews that way.  Now ideally you don’t want a green that skews either way, and this one is very very close to the target.  Depending on the accuracy of the white balance it’s either dead-on, or just a hair away from yellow.  I’m cool with that, and prefer it to most of the other paints I’ve tested that are either dead on, or skew a bit towards yellow.  This “playing it safe with the yellows” is also why I like the Ultimatte paint if you’re looking for something with a hotter exposure and more vivid saturation, albeit at a bank-breaking price.

Let me know if any of this info is useful or if you have anything to add.  If anyone does put some of this to use, please let me know!