Film - A Practical Guide to Video and Audio Compression - page 43

4

Film

4.1 The Traditional Route

On our journey through the complexities of video compression, we now look at movie
film. Film has been around for a while. It was the first kind of moving image to be
recorded, so we could think of film as a classic or traditional format.
TV has been with us for many years, too, but film has been around much longer.
Most major studios have been in existence for 80 years or more, and the technology existed
for some time even before Hollywood became properly established.
So for this part of our trip, we'll look at how film technology creates those images
flickering on the movie screen, which will help us understand the other formats better
when we get to them.

4.2 Back in the Old Days

Film stock and camera manufacturers have made some significant improvements in what
can be accomplished with movie film. The most problematic aspect of film is that because
a chemical reaction imprinted the images, the film ages; that is, the images will degrade
with time. They will lose contrast and the color will shift because each emulsion on the
film substrate ages differently. This applies equally to films made by Hollywood movie
companies and to those home movies shot in the 1950s and `60s on 8 mm film.
Recovering and restoring some of our older footage and archiving it in a digital form
are vitally important. If we neglect to do this over the next few years, it will be gone forever.
In this chapter the important aspects of film are examined. Knowing about the nature
of film will help you get the most out of the compression process if this is where your
source material is coming from.

4.3 How Film Projectors Work

Projectors and cameras transport the film in the same way. The camera simply uses a
slightly larger shutter aperture than the projector. Many alternative mechanisms were

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