What’s old is new again.
When I watch shows like The Mandalorian and learn about using the volume, it becomes apparent that such methods conceptually stem from the earliest days of film. Some of these old school techniques are still in use today.
Rear-screen projection draws the most direct line to the volume. In its simplest form, there’s a translucent screen behind the talent. Imagery is projected from behind onto the screen. The camera sees the actors against this background scene as if that was a real set or landscape. No compositing is required since this is all in-camera. In old films, this was a common technique for car driving scenes. The same technique was used by David Fincher for Mank. Instead of projected images, large high-resolution video screens were used.
Front-screen projection is a similar process. The camera faces a special reflective backdrop coated with tiny glass beads. There’s a two-way mirror block between the camera lens and the talent who is standing in front of the screen. A projection source sits at 90 degrees to the camera and shines into the mirror, which is at a 45-degree angle inside the block. This casts the image onto the reflective backdrop. The camera shoots through this same mirror and sees both the talent and the projected image behind them, much like front screen projection.
The trick is that the projected image is also shining onto the talent, but you don’t actually see it on the talent. The reason is that the projector light level is so low that it’s washed out by the lighting on the talent. The glass beads of the backdrop act as tiny lenses to focus the light of the projected background image back towards the camera lens. The camera sees a proper combination without contamination onto the talent, even if that’s not what you see with the naked eye.
A similar concept is used in certain chromakey techniques. A ring light on the camera lens shines green or blue light onto the talent and the grey, reflective backdrop behind the talent. This backdrop also contains small glass beads that act as tiny lenses. The camera sees color-correct talent, but instead of grey, it’s a perfect green or blue screen behind them.
Aerial image projection is a cool technique that I haven’t personally seen used in modern production, although it’s probably still used in some special effects work. The process was used in multimedia production to add camera moves on still images. In a sense it led to digital video effects. There’s a projection source that shines an image onto a translucent, suspended pane of ground glass. A camera is positioned on the opposite side, so both camera and projector face the glass pane. The projected image is focused onto the glass, so that it’s crisp. Then the camera records the image, which can be resized as needed. In addition, a camera operator can add camera moves while recording the projected image that is “floating” on the glass pane.
©2022 Oliver Peters