The Green That Wasn't

It was the kind of shoot that looks simple on paper. One singer, one afternoon, a green-screen studio booked for six hours. The plan was to put her inside a candy-coloured world we had already built in 3D. All we needed was a clean performance against green.

We arrived early. The cyclorama looked perfect: freshly painted, even, bright. The lights went up, the camera came out of its case, and while the crew set up, the singer went to wardrobe.

She came back twenty minutes later in the dress the stylist had chosen weeks before. It was beautiful. It was also, unmistakably, mint green.

The silence on set

Nobody said anything for a few seconds. Then the gaffer laughed, because that is what gaffers do when a problem is too big to solve with a flag. Anyone who has keyed footage knows what happens next: every pixel of that dress would disappear along with the background, and our singer would become a floating head with arms.

There were three options, and none of them were good.

• Change the dress. The stylist had nothing else that matched the look the artist had approved.
• Shoot anyway and rotoscope. Frame by frame, by hand, for a three-minute video. Weeks of work we had not budgeted for.
• Change the screen. We had no blue screen, and the studio didn't either.

The fourth option

The solution came from the camera assistant, who had been quiet all morning. "How green is the dress, really?" he asked.

We put the dress in front of the screen and looked at it on the scopes instead of with our eyes. On the monitor it read as green. On the vectorscope, it sat clearly apart from the screen: lighter, less saturated and leaning towards blue. Different enough to separate, if we were careful.

So we were careful. We lit the screen a little darker and the singer a little hotter, so the two greens moved further apart. We pulled her two metres further from the background to kill the spill. We shot a test, keyed it on a laptop right there on set, and watched the dress survive.

It wasn't a perfect key. There were a few shots where the hem needed a garbage matte and some patient cleanup. But the video was finished on time, and the dress, the one everyone had approved, stayed in it.

What I took from it

The lesson is not "check the wardrobe", although you should check the wardrobe. The lesson is that your eyes are the worst tool on a green-screen set. They adapt, they lie, and they panic. The scopes don't.

Since that day, the first thing I do on any keying job is put every costume, prop and piece of hair in front of the screen and look at it on a vectorscope before anyone rolls camera. It takes five minutes. It has saved me weeks.

And I never again let a stylist's mood board arrive on set without a colour chip next to it.