Beyond Keylight: Better Mattes

Beyond Keylight: Better Mattes

So, to recap, the number one thing you can do to improve
a matte is to break it down into component parts:
. Garbage, Core, and Edge mattes (isolate the threshold
areas)
. Holdout masks for problematic areas of the frame (big
hair, fast motion, varied lighting, and shadow)

. Temporal split (if light conditions change as the shot
progresses)
All other tricks fall short if you’re not willing to take the
trouble to do this. Here are other steps to take to ensure a
good matte.
On Set
Your time is often considered cheaper than that of a full
crew on set—in many cases, justifi ably so. That means—
shocking, I know—you’ll be fi xing things in post that
shoulda coulda woulda been handled differently on set. If,
on the other hand, you have the opportunity to supervise
on set, knowledge is power.
A hard cyclorama, or cyc (pronounced like “psych”) is far
preferable to soft materials, especially if the fl oor is in shot.
If you can’t rent a stage that has one, the next best thing
might be to invest in a roll of fl oor covering and paint it,
to get the smooth transition from fl oor to wall, as in Figure
6.28 (assuming the fl oor is in shot).
Regarding the fl oor, don’t let anyone walk across it in
street shoes, which will quickly contaminate it with very
visible dust. There are white shoe-cover booties often
used specifi cally to avoid this, and you can also lay down
big pieces of cardboard for the crew to use setting up. Be
pedantic about this if you’re planning to key shadows.

Lighting is, of course, best left to an experienced Director
of Photography (D.P.) or gaffer (one who has shot effects
before is hugely helpful), and any kind of recommendations
for a physical lighting setup are beyond the scope of
this book. Because you’ll spend more time examining this
footage than anyone else, here are a few things to watch
for on set:
. Light levels on the foreground and background should
have matching intensity. A spot light meter tells you if
they do.
. Diffuse lights are great for the background (often a set
of large 1 K, 2 K, or 5 K lights with a silk sock covering
them, but fl uorescent lights will do in a
pinch, on a smaller set. With fl uorescents you just need
more instruments to light the same space. Kino Flo
lights are a popular option for smaller sets as well.

. Maintain space between the foreground and background.
Ten feet is ideal.
. Avoid unintentional shadows, but by all means light
for shadows if you can get them and the fl oor is clean.
Note that this works only when the fi nal shot also has a
fl at fl oor.
. Where possible, avoid having talent sit, kneel, or lie
down directly on the fl oor or any other keyable surface;

not only does an astonishing wash of shadow and refl ection
result, but there is no realistic interaction with the
surface, which is especially noticeable if they are to end
up on carpet, or grass, or the beach. If possible, use real
surfaces and furniture in these cases.
. Here’s a novel idea: Shoot exteriors outside where possible,
forgoing the cyc and controlled lighting environment
for chromatic tarps and the sun, which is a hard
lighting source to fake.
. Record as close to uncompressed as possible. Even
prosumer HD cameras these days almost always have
an HDMI port that outputs live, uncompressed signal;
pair this with a workstation or laptop containing a video
capture card and high-speed storage and you can get
4:2:2 or better practically for free.
. Shoot clean plate: a few frames of the set only, particularly
on a locked-off shot and each time a new set-up
occurs.
In this day and age of quick camera to laptop transfer, it’s
great to have the means on-set to pull test comps; they not
only help ensure that the result will key properly, they give
the D.P. and talent a better idea of where they are, and
where they can lead to more motivated light from the D.P.
and more motivated action from the talent, who otherwise
must work in a void.