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Sunday, April 4, 2010

Volcanic Getaway

The volcano is now in full eruption, and as ash and rocks begin to fall, our intrepid hero turns to make his escape. Luckily, we already have footage of a volcano, but now need a shot of hero interacting with it. How to do this with the method described in last month's posts ?

Let's say the film is being made on Super-8 and the volcano footage is on 16mm. It's been taken obviously with quite a long lens, is well-exposed and acceptably steady, though maybe not rock-steady. A 16mm projector is set up with an old super-8 camera connected to it by a flexible shaft. It doesn't matter what speed the camera normally goes at, the projector will run the camera at its own speed, let's say 24 fps. We project onto a decent normal screen say 4 feet wide. This should be possible with fast lenses and film. Certainly 3 feet is no problem for brightness. Scotchlite screens are not necessary for this type of set-up. The camera is positioned some distance to the side. Our hero begins his turn in a position that just misses the projected rays. He is lit by two or three spotlights so that no light falls on the screen. Slide projectors with defocused lenses will work just as well. Some ambient light on the screen doesn't usually matter. Hero starts to run towards camera with polystyrene or papier mache rocks etc falling about him. A medium tele lens setting on the camera enhances the feeling of danger as the volcano appears nearer to the character, as well as matching the perspective. Hand-holding the super-8 camera will add realism, also helping to mask any unsteadiness of the background shot. You could maybe overcrank the camera a bit ? ie. say if the rest of the film is being shot at 18 fps, 24 fps will slow the action somewhat. The main thing that is so important to get right for any effects shot like this, is the colour filtration on the foreground lighting. It must match the background projected plate, or the audience will smell a rat.

Two more points worth mentioning...
When you copy a film there is always some loss of quality, so it makes sense to have the background plate made on higher resolution film-stock than the filming stock. In this example the problem is easily overcome by using 16mm versus the smaller super-8 format.

What about focusing ? Using wide apertures there will be less depth of field, but probably enough to play with. This is one of the unsung virtues of Super-8, so much depth of field... it's a godsend (especially when working with miniatures). However, if you did have a focusing problem you could perhaps do a fast focus-pull from the volcano to the hero.