Acting with blue screen mattes is a part of filming that is thought to be especially difficult, since the thing that you are looking at is just a cross on a wall or a stick with a blob on top. Whether you are supposed to be reacting to the majesty of a nineteenth century Brazilian opera house or your beloved being thrown from a parapet, an alien making pancakes in your parent's kitchen or a unicorn guiding you through an enchanted forest, the blue screen stays pretty much the same; a big blue backdrop, just hanging there. Lately it is more likely to be green, but still, it doesn't emote much. Of course, neither does the camera lens or the theatrical backcloth, but you will still spend many hours staring at bits of Gaffa tape stuck to the inside of a lens hood or gazing out of a window frame at a third of a tree stump stuck in a bucket in front of a painting of a forest. (On one film I was in the director was so in love with the other actress that he couldn't bear to have a shot without her in it. Thus, all my close-ups were organised with her reflection over my shoulder while I would talk to a light stand. As she was both incredibly beautiful and disconcertingly lovely, I only minded a bit.)
When we were filming 'Dinotopia', there was an enormous amount of green screen work, and one of the sound stages was entirely painted the requisite shade of green. There were flight sequences and mountain top scenes and machines developed to simulate the stride of different dinosaurs, so that when you sat in the saddle (very high up) and the right programme was set, you could be on a larger or smaller dinosaur, walking or running. If the wrong programme was set it was not unlike riding a mechanical bull. (Yes, I have, once with a lot of tequila.) A great deal of thought had gone into the dinosaur-riding machine, but you couldn't stay on it for very long without throwing up, dinosaurs are an awkward taxi. But the main problem with dinosaur filming was the great variety of heights. In a scene with a triceratops, a couple of diplodocus (diplodoci?) and some veloceraptors, there were only so many sticks with blobs on that could be set up. The amazing special effects team at Framestore must have had a terrible time fixing the eye lines in editing.
My earliest memory of filming with blue screen was the 'Chester Mystery Cycle Plays' for the BBC. I was 10 and playing a type of seraph and spent some days milling around the studio at Woodlane with a pair of wings and a halo. As I remember there were a lot of set pieces and plenty of time to observe the surroundings. When I came home my parents asked how it was all going. "God was lovely." I said, "And Mary gave me a cup of tea. But I don't like the Devil much." "No" said my dad, "I know what you mean."