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The world according to the Blaine Brothers: Luma Key

We've heard already that the Blaine Brothers avoid green screen when they can. In this interview they explain how they use Luma key instead.
I was looking at Skyfall, where they’ve added breath in some of the scenes on the end. And they use kettles. And they’re filming steam coming from a kettle. Well, why are you using steam from a kettle? Because that doesn’t look like it’s coming from someone’s mouth. Why don’t you just film steam coming from someone’s mouth? Which is what we did in the end, which was quite tricky to do. But actually, what I think worked better than Skyfall, which is quite a nice thing to say. With the breath, again, it’s that thing of like, you first did that. And you stuck it on. And it’s like, oh, that still looks really fake. And you go, well, yeah, but play with it.
And then manipulate it and change the opacity of it. And suddenly, you’re like, oh yeah, actually. And again, it’s the interesting thing that, like, with the breath in particular, as I [INAUDIBLE], like, looking back at, like, the couple of moments of actual breath and realising how little of it you actually see. Yeah. And you got it right down, so it was almost like, all of that work, and it’s hardly there. And you’re like, yeah, but it’s there enough. And you’re like, that’s all I need. I now totally– I buy that, that that’s totally real. Doing the breath was done by saying the lines along with them. So– Like ADR.
Yeah, like doing ADR, where if the sound isn’t right, then you’ll get the actors to repeat the lines in sync. And they just keep going around the loop until they’ve got in sync with the line. And then great, you’ve got a nice clean recording of that. And you’re putting that into the film. And then doing exactly the same thing but with, yeah, being incredibly cold. [BREATHING] So he’s gone. He stopped texting.
So he’s gone. He stopped texting.
So he’s gone. He stopped texting.
I tried first off just filming myself talking. But obviously, I’ve got a white face. And you trying to cut me out is actually quite hard. But all you really need to do is a Luma Key. You’re just trying to get the white breath, and that’s all you want remaining. So I actually painted myself black and then realised my nose was sticking out. So I taped my nose down. And then, yeah, so you’ve just got a couple of back lights. And just outside on a cold day, I was waiting for a really cold day where there’s a lot of moisture in the air.
OK. So here we go. This is a shot, which is at night on a draw carriageway. And it’s going to be cold. And it’s not actually that cold– not cold enough to get breath. So we’re adding breath to it. So basically, you see all of these crazy squiggles that are going on. That one makes some sense, whereas these ones don’t seem to. But what these are actually doing is drawing around little parts of breath. So loads of lines drawn all around, and that’s basically on this layer here. And I’ll show you what that layer actually is going on. So that’s actually me breathing.
So getting some breath in, and then on the composition, there I am, as if I was breathing. But obviously, by putting the masks in, suddenly, we’ve just got this bit here. So that’s coming out of Holly’s mouth. So I also need to put her in front of it. So I’m cutting around her and him so that their breath is behind. And yeah, so we’ve done a lot to push it down. So, like, in terms of opacity, the opacity of it is way down. It’s 37%. And I got blur going on on it and also some photo philtres so that I’m warming up the breath so that it looks the same colour because everything’s underneath tungsten light.
And what I’ve done with the breath here is I’ve deleted, or rather, I’ve got rid of all of the colour. So I’m not having to worry about saturation. It’s just literally a Luma Key. And then I can affect how the actual colour of the breath looks when we get into the other side.
So a slightly different version of the breath– I shot quite a few times to try and get the breath looking right. And yeah, so the first one you’re looking at, you’re seeing that. And that’s me in bright daylight. So that was a particularly cold day. And the back light, that’s coming from the sun. And I’ve just put up a black sheet behind me so that I can Luma Key the white out. Whereas, this shot I shot at night. And there’s some back light going on. And I’ve deliberately tried to make me look as dark as possible so that I can get the breath as close around me as possible. So yeah, so there’s a lot of version of this.
But that’s effectively the idea. And the other thing– we’re trying to make the breath look correct is by drawing a load of shapes. I’m changing the opacity of it and only showing it where I want it to be, as well. So there’s quite a bit of animation going on to try and make it look exactly how I want it to. So if I turn off the masks on this one, so you see, that’s me behind there with, yeah, face blacked out and also with a bit of tape over my nose so that it’s not getting hit by the back light.
Because he’s in shadow here, you’re going to get more light coming from this side over here than you are on this side. So this side, the opacity’s less. This side, you’re getting it a bit brighter because you’ve got back light. And that’s what is going to make it feel real is the fact that if you’re seeing breath, the reason you’re seeing it is because there’s a big strong light behind.

Let’s move a world away from the blue screen excess of “Sky Captain”. We know it’s not always necessary to key on a colour. Atmospheric elements like smoke, clouds or breath can be achieved by resorting to luma key, in other words keying on the brightness of an image. Here we see how the Blaine Brothers used luma key to create a very chilly atmosphere for their horror movie Nina Forever.

Note there are no gory clips in this interview.

Chris Blaine goes to extraordinary lengths to get the ‘cold breath’ look, and invents a strange variant of Automatic Dialogue Replacement (ADR) – the process in which voice sounds are recorded in post production, but for breath! Note also how in the end he makes it subtle so it’s just adding to the atmosphere instead of drawing attention to itself and exaggerating the moment. Also he mentions he’s got rid of the colour or saturation of the originally shot breath so he doesn’t need to worry about how it might be the wrong colour hue for the shot it is being transplanted into

Can you think of other examples of when you might use luma key? It’s obviously easier than using green or blue, but the disadvantage is it’s sometimes not as precise. With smoke or steam against a black background that’s not an issue. When else might you use this more basic technique? Or could you see Chris’s rather strange technique as being useful to you? Tell us your ideas in the comments below.

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