05 shooting for effects

1
05 shooting for effects
DAD141P Principles of Basic Video Editing and
Production
2
Shooting for Effects

• Chroma key (also referred to as blue screen or
  green screen) involves shooting a person or
  object in front of a colored screen, then using
  an effect to remove the colored screen from the
  shot and replace it with a substitute background.
  
• The particular screen colors, highly saturated
  blue or green, are used because they don't show
  up in nature regardless of a person's skin tone,
  you'll never see someone who looks that blue or
  that green.
• In postproduction, a technician identifies the
  color of the blue or green screen in a shot, and
  then removes that color from the footage. This
  process is called keying.
• When you key out, or remove, a color using a
  non-linear editing system, all the pixels
  containing that color become transparent.

3

• In the first image above left, a boy stands in
  front of a chroma key screen the second photo
  depicts a street scene he will be composited
  into the third image shows the boy composited
  into the background clip.
• Because the keyed clip now contains areas that
  are transparent, any still or moving image the
  technician adds as a background clip will show
  through. The process of combining two (or more)
  video images into one is called compositing.

4
Preparing a Chroma Key Shoot

• Creased backgrounds can be a problem for chroma
  key effects because the creases produce shadows,
  making some areas darker and others lighterthis
  results in a multicolored background instead of a
  solid color background
• Solid backgrounds are easier to key out, because
  they contain only one color to identify and
  remove.
• Just as a crease-free background makes chroma key
  effects easier to execute, so does evenly
  lighting your background. Even if you work with
  the perfect solid-color background, shadows or
  inadequate lighting can make key effects more
  difficult, if not impossible.

5
Lighting your Chroma Key shoot

• The background
• Similar in color to darker areas of your actor's
  hair or wardrobe will key out pieces of your
  actor along with the chroma key background you're
  trying to remove.
• To light the chroma key background we placed very
  powerful 600-watt tungsten lights at either end
  and positioned them to light the background as
  evenly as possible.
• The actor
• Once you have your background evenly lit, it's
  time to light your actor, preferably without
  casting shadows on your background.
• One preventative measure you can take is
  positioning your actor at a distance from the
  background
• This not only helps prevent shadows, but it also
  helps to prevent the color of your screen from
  reflecting, or spilling, onto your actor.

6
Wardrobe, hair, and smoke

• Cleaner edges yield cleaner key effects.
• A person with neatly arranged hair is much easier
  to key out of a background than a person with
  wild wisps of hair going off in every direction
• Shaggy wardrobe materials, like a fuzzy sweater,
  a fleecy jacket, or clothing with fringes can be
  especially hard to work with as well.
• Some types of dangling jewelry, such as fine
  strands of gold in a necklace or earrings, can
  also be problematic .
• If you're not sure, do some tests. Shoot some
  footage of your actor in a dress rehearsal, and
  try out the composite techniques you'd like to
  use.

7
Framing Images with Composites in Mind

• Just as the shadows and lighting in your key shot
  need to match the shadows and lighting in your
  background, the content and framing of your
  foreground clip needs to work well enough with
  the background clip that the combination is
  believable
• If you shoot an actor against a blue or green
  screen and then key out the background, it's
  often easier to composite her into a shot if you
  don't show her entire body
• Likewise, if you're compositing an actor into a
  landscape or street scene, it becomes harder to
  composite the actor in a way that looks plausible
  if you show his entire body.
• A good solution is to compose a more close-up
  shot, perhaps showing him from the waist or chest
  up. That way, the actor looks like he's in the
  foreground of your frame, with a realistic
  looking background behind him.

8
Planning a Matte Effect

• A matte effect defines an area of the screen, in
  the shape of your choice, that becomes
  transparent and enables another video image to
  show through.
• The shape that defines the transparent area is
  called a matte.
• In ready made matte effects you can apply as
  filters to create round, square, or
  diamond-shaped mattes.
• Garbage matte create custom matte shapes using 4
  or 8 points on the screen.
• You can use a travel matte to create a matte
  effect in the exact shape of a complex graphic
  you've produced in a program such as Photoshop or
  Illustrator.

9
Composing reflections

• Plan and compose a good close-up shot to use as
  your reflection.
• Record the close-up as large as you can (don't
  try to record the shot at a size small enough to
  fit into your target).
• Shrink the shot down to the target size using the
  scaling tools in Final Cut, Premiere, or After
  Effects (working at full size and then shrinking
  an image provides you with much more detail and
  control than attempting to shoot something really
  small).
• To make the reflections look more realistic, and
  less like something you pasted in, try different
  composite modes
• Composite the reflection clip into al target
  areas, that way, if the reflection contains
  movement, the action will be the same on the
  other targets.

10
Working with a tripod

• Working with a tripod allows you to shoot stable
  images and take full advantage of the control
  these digital systems afford you as a director.
• It almost seems ironic, but even though you have
  all this computer power at your fingertips,
  something as low-tech as a tripod can make or
  break your shot.
• If you plan to add a matte background, using a
  tripod will make your life significantly easier.

11
Thank you