1 The Director of Photography – an overview

96 Practical Cinematography
camera negative. If we sample in a linear pattern, the 11-stop dynamic
range of a modern camera negative will need a 13-bit file to hold all
that data using 0.002 intervals of density between samples.This means
that, in order to get sufficient data for the shadows to look real, there
must be 8192 options of recordable brightness for each pixel.
However, if a tonal range of 11 stops on the camera negative is sampled
in a logarithmic way, the same amount of necessary information
can be recorded on a 10-bit file, which has only 1024 options. This
means much smaller files are needed but the audience will still see an
image of equivalent quality.
Image acquisition
At the start of the DI process it is necessary to scan the photographic
image so that we can write it in the binary code. The most important
decision is what digital resolution we use and this is described by
referring to the number of pixels the horizontal width of the picture is
broken up into.There is much discussion in the post-production world
as to how many horizontal pixels are needed, with almost as many
opinions as there are post-production houses, so I am going to give my
opinion, and I have taken very good advice on this.
A 35 mm master camera negative is almost universally agreed to have
the equivalent of a digital image of 4000 pixels horizontally.Therefore,
if you wish to take a shot, manipulate it digitally and return it to the
cut camera master negative, you must scan at 4000 pixel resolution in
order that no discernible degradation in picture quality occurs when
you make the photographic intermediates.
If you are going to scan your camera master and do all your intermediates
digitally, only returning to film for the release print, or at the
worst the intermediate photographic negative, then scanning your
original at 2000 pixels horizontally will be enough and can produce an
image on the cinema screen every bit as good as the purely photographic
method described above.
Incidentally, we refer to a picture with 4000 horizontal pixels as having
a 4k resolution and one with 2000 pixels as 2k.
Why the difference? The traditional route from camera master negative
to the cinema release print usually looks like this:
1 Camera negative – printed to intermediate positives.
2 Intermediate positive – printed to intermediate negatives.
3 Intermediate negatives – printed to cinema release prints.
4 Cinema release print – to cinema screen.
It is an inescapable fact that every time you make a photographic copy
you must lose some picture quality; therefore, if you go through this
process starting with 4k camera negative you will end up on the screen
with something having a poorer resolution.
To satisfy the resolution of an audience sitting in the optimum viewing
position in a cinema, the screen picture quality must have a horizontal
resolution equivalent to 1000 pixels or better. Only then will
they consider the image to be sharp. In order to achieve this, one must
start with a camera negative having a 4k resolution and that will, after
the degradation due to the copying process, give roughly a 1.2k image
on the cinema screen and this, therefore, satisfies the audience criteria.