Friday, December 28, 2007
There were a lot of things in the production of this movie that were responsible for it's rich tapestry of looks, but it is all too easy to forget that no post production took place.
While Roger Rabbit had the optical printer, the Thief came straight out of the camera, the way it was shot.
Also in the city, there lived a thief who shall be nameless...
Also in the city, there was some birefringence, which shall be called the Sellotape trick.
I am talking here about, what in computer terms is called, colour cycling.
The effect of coloured patterns cycling through all the hues in relation to each other is probably best known from the swirling background in the "Return of the Pink Panther" titles, but I think I am correct in assuming it is also responsible for the water effect in the fountainand most definitely the treatment of all the "gem effects" throughout the film.
Here's how it works:
The cameraman shoots the whole scene, camera-moves and all, but with the water area of the fountain painted black.
Film is rewound and the same move is shot again on the same piece of film, this time with a matte (black card or painted cel), the shape of the water surface, on the camera light box.
Behind the matte is a polaroid screen, (polarizing filter) that covers the matted area.
On top of this screen is a cel with the shapes of ripples stuck on from various layers of clear sticky tape (Sellotape in the UK).
Some 5 or 6 layers of tape have to be applied to get nice strong colours, so the whole shebang can become quite thick, which doesn't matter as it is all backlit and shadows are not an issue.
To the naked eye, this is still totally devoid of colours, but when seen through a second polaroid screen, turns into a veritable aurora borealis.
The second screen can either be a motorized filter that rotates on the camera or a second screen, applied to the top of the matte, the only important thing being that the cel with the tape is between the filters.
Polarizers restrict the light that falls through them to wave action in one direction only, that means, if you put a horizontal polarizer on top of a vertical one, virtually no light penetrates, rotate the top screen to horizontal and the screens become clear, the principle behind the display on your pocket calculator.
Stretched polythene, such as cling film (Ceranowrap) and sticky tape, has the weird property of twisting light that falls through them, but, and here is the trick, not all colours by the same amount.
So if for example enough layers are applied to twist red through 90 degrees more than green, than, with the filters above and below at right angles, no green penetrates, but red goes through unhindered.
If the top filter is allowed to rotate, the generated colours cycle through their respective hues.
A colour filter would be added to tint the whole effect. Blue, in this case.
The process is called birefringence, but we never called it that of course.
If any Rostrum camera person out there knows what they called it, please enlighten us.
There are added back lit water effects on top of these two exposures and there would probably have been some top lit effects as well but I'm sure we will come to some of those techniques later when we arrive at (what Dick called) the Star wars scene.
If you have children and come back from the Imax 3-D one day, with your pocket full of cheap cardboard 3-D glasses, get the Sellotape out and have some fun...
Your kids'll love it...