Lighting Techniques
In lighting there are two goals: get enough light; use the
light you have to shape and define objects in the scene. Lighting
is often tried out "on paper" by using a lighting
diagram before it's actually set. Many potential problems can be
spotted in the process of constructing a lighting diagram. The
most common of these is to light for a theoretical "stage
front" instead of lighting for specific camera positions.
It's also useful in anticipating problems with shadows falling
where they're not wanted. Every light casts a shadow. The
lighting diagram will make it easier to see where those shadows
might fall.
One man, One Camera
The simplest type of lighting involves one camera shooting one
subject. The subject is placed in the setting far enough away
from any walls or backdrops to avoid casting shadows on the
background near the subject. The camera is set up placing the
subject in front of the backdrop.
Key Light
The first light set is usually the key light. It's positioned
thirty to forty-five degrees to the side of the camera and should
strike the subject at an angle of about forty-five degrees from
vertical. This lighting angle is best for people with normal
features. People with short noses or weak chins should be lit
from a steeper angle to increase the length of the shadows cast
under the nose or chin. Those with long noses should be lit with
less angle to produce shorter shadows. Moving the light closer to
the camera will reduce the amount of modeling in the face and
make the subject appear heavier than he is. Conversely, moving
the light farther from the camera will throw more of the face in
shadow, making it appear narrower. The key light is focused on
the subject by putting the bulb in the "full spot"
position and centering the beam on the subject. The light is then
flooded out until a reasonable overall level is reached.
"Reasonable" means you can generate sixty to seventy
IRE units of video on faces with minimal video noise in the
picture and enough depth of field for your purposes.
Back Light
The back light is placed directly behind the subject, in line
with the camera. It, too, is set at a forty-five degree angle
from vertical. The back light is spotted down and aimed at the
subject's neck. It is then flooded until it has about the same
intensity as the key light. The back light should be adjusted to
produce a crisp but subtle border around the subject. People with
blonde (or missing) hair require less intensity. People with very
dark hair require more. When the back light is still too bright
in the full flood position, a scrim can be fitted in front of the
housing to soften and reduce the light.
Fill Light
Fill light is added on the side of the camera opposite the key
light. Fill light should be about half the intensity of the key
and back lights. It should also be softer, producing no harsh
shadows. Often a broad, scoop, or soft light is used instead of a
spotlight to provide fill. Fill lights are also frequently
scrimmed to soften them and reduce their intensity.
Background
Finally, background light is added to bring the background up
to a level in the middle of the overall gray scale of the
subject. Background lighting should be even and unobtrusive. The
background shouldn't be made the center of attention with harsh
or uneven lighting.
Movement
But what if the subject moves? Depending on the movement, there are two
ways of handling this problem. Suppose the subject moves from one
important area to another along a pre-determined path. It is neither
necessary nor desirable to provide full key, back, and fill along the
entire path. It is necessary only to provide about the same overall
illumination along the path of travel. This may be accomplished either
by making sure the lighted areas overlap sufficiently that no drop in
level will be detected by the viewer, or, where distances are greater,
by adding sufficient fill along the path to keep the level reasonably
constant. In general, back light for a movement from one lit area to
another isn't necessary.
When movement of the subject is likely to be random or to cover too
large an area of the set, it is possible to provide a diffuse fill
lighting to the entire area. This is commonly called "base light" and
is designed to keep all shadows within acceptable contrast range. Key
and back lights are then added for specific areas and camera positions
as necessary. While this kind of lighting might be helpful in certain
situations, it generally results in a flat and dull overall appearance.
Since every light used creates its own shadows, this technique can also
result in multiple shadows detracting from the modeling effects
rendered by a more orthodox application of key, back, and fill
techniques.
Cross Lighting
When a quick and simple lighting plan is needed, cross-lighting is
usually the best approach. Adjustable spotlights are placed in the
corners of a room, flanking the intended camera position. Because they
must "throw" their light some distance, they should be adjusted for a
narrow beam (spotted down) and aimed in a crossing pattern at the
opposite corners. Unfocused light loses its power with the square of
the distance from the light. Normally this would make foreground
subjects too bright and background subjects too dark. By spotting the
lights and aiming them at the corners, the loss of light with distance
is minimized and the narrow spread of the beam reduces the amount of
light striking foreground subjects.
Lighting for Dance
In some cases, even the standard television lighting is too flat for
the desired effect. The most prominent example of this situation is in
dance. While dance suggests an even illumination of the entire set, it
is usually desirable to create shadows that show off the dancers' form.
This is done by lighting from greater angles than normal. There is
often little or no light from the direction of the camera. Instead,
lights are placed at from about seventy to ninety degrees from the
camera position. Back light, too, is steeper than normal.
Of course, the mood and artistic objectives of the dance have to be
considered. It's possible that standard television lighting would be
appropriate for some dances, especially those involving elaborate
costumes or an emphasis on story or drama. More radical lighting might
be suggested by dance emphasizing the form and movement of the human
body. Steeper lighting does create larger areas of shadow, and widening
the difference in intensity between key and fill lighting, even
eliminating fill lighting entirely, does heighten the sense of energy
and tension important to some ballet and modern dance.
High Contrast
The technique of eliminating fill lighting, leaving only key and back
light, is called "high contrast" lighting. While it may be appropriate
for some forms of dance, its use in other contexts should be sparing.
Not only can it easily be overdone, but it also tends to aggravate some
technical shortcomings in low-cost cameras and recorders. Any tendency
for the picture to "lag" will be made unbearably obvious and areas of
the picture left too dark will show video noise generated by cameras
and recorders with limited signal-to-noise and noise reduction
characteristics.
Limbo
Limbo lighting, like high contrast lighting, poses technical problems
for less sophisticated equipment. In limbo lighting normal key, back,
and fill lighting or high contrast lighting is used, but great care is
taken to eliminate any light from the background or floor behind the
subject. The intended effect is to leave the subject without any visual
context. The more likely effect in analog recordings is a context of
video noise, especially if recording or editing for later distribution
is intended.
Back lighting
Back lighting is generally used in the attempt to conceal the identity
of people on camera or to provide an "interesting" background for
program titles and credits. Key and fill lights are eliminated, leaving
only back and background lights. Because of the large amount of stray
light bounced off of floors and walls, back lighting doesn't completely
eliminate "fill" light on the subject and may not therefore provide
sufficient anonymity for the subject.
Application
Standard television lighting is basically key, back, and fill. As you
look around the real world, you would be hard pressed to find a single
example of this rather artificial scheme. So how does this technique
apply to you?
I remember still photographers on a trip to Panama years ago saying "I
hate this light." or "The light isn't right yet." What they hated was
the high angle of the tropical sun at midday. They wouldn't like the
light until the sun fell to about a forty-five degree angle, or the
proper angle for a key light. Outdoors the sun is the key light. North
of the tropics, the sun is at a good angle in mid morning and mid
afternoon. I've often taken one look at a building and decided whether
to record it in the morning or afternoon. I've also selected the camera
position to put the sun in the right place in relation to the camera.
Outdoors, the content of the sky is very important. Obviously, dark
clouds and rain don't do much for a positive image. But even a light
cloud cover or haze can make a profound difference in your pictures. On
a clear day, a sunlit structure will be brighter than the sky. You can
throw a couple of nice clouds into the background for effect, but
basically the blue background is darker than the sunlit subject. Light
haze and clouds will almost always be brighter than the subject. They
could make the White House look like a medieval dungeon.
Striking pictures, whether still, film, or video can be made using the
sun as a back light, or by playing with the angle between the camera,
subject, and sun. If you remember where the key light is in
conventional lighting, you can use it as a guide to shooting outdoors,
both by following and by breaking the rules.
Office lighting generally runs from fifty to one hundred foot candles.
Obviously plenty for good pictures. Unfortunately, all of those
fluorescent lights point straight down. Eye sockets are turned into
black holes. Lights in the background are brighter than the subject.
I've found that the cross lighting technique we mentioned can provide
key and fill lighting in the typical office environment. It throws
enough light on the back walls or other distant objects, and provides
the modeling that would otherwise be missing. The fact that the
background light is at 4500 degrees Kelvin while the key and fill
lights are at 3200 degrees Kelvin doesn't seem to cause a problem, as
long as the camera is white balanced for 3200 degrees Kelvin.
Lighting and Image Resolution
In creating video images we want to produce pictures that appear sharp
and clear without being harsh. Spotlights have traditionally been
used as key lights to provide clear, crisp images with video formats
that lacked resolution. Although industrial and broadcast cameras
have generally had resolution superior to the broadcast signal, the
same cannot be said for videotape. While the calculated
resolution of broadcast television is around 330 horizontal lines, VHS
tape has a resolution of about 230 to 240 lines. Betamax and
¾ inch U-Matic tapes were 240 to 260 lines. With the
advent of S-Video both consumers and professionals could record at a
better-than-broadcast 480 lines of resolution. Now DV (digital
video) offers a calculated 530 lines of horizontal resolution and high
definition television can deliver more than twice that.
As resolution improves, traditional television lighting tends to be
harsh and unflattering. To adjust to this change in technology,
some broadcast news sets are now lit by banks of soft lights.
Others still use spotlights, which tend to exaggerate facial creases
and wrinkles. This is especially unfortunate for people with thin
faces. With the increased sensitivity and resolution, we can
sometimes employ techniques more common to still photography.
Bouncing a spotlight off of a silvered umbrella, for example, will
create a much softer light that is more flattering to people. We
will have to work with additional changes to both lighting and makeup
as we move to high definition video.
That “Homey Look”
Homes are comfortable, friendly places. They are warm and nurturing.
Broadcast television spends a lot of time and energy trying to mimic
the "homey" look, whether in daytime dramas or situation comedies or
talk shows. As you look around your own living room, here are some of
the concerns the network producer might have in reproducing "the look."
The most important means of avoiding the "studio look" is to simulate
more conventional room lighting. That is not to say that normal room
lighting should be imitated. Rather, the effects of room lighting
should be examined and recreated for the camera. These effects fall
into two broad categories.
The basic area illuminated by room light is normally at the level of
table lamps and below. Light normally falls off toward the ceiling. By
aiming lights and using barn doors to reduce the amount of light near
the top of the set, this effect can be imitated. Even though lighting
angles are those of conventional television, the viewer will associate
lighting with those lamps found in his normal environment, provided
reasonable diffuse fill light is combined with key and back light that
doesn't create hard and distracting shadows.
Next, key light positions may be modified and adapted to represent
visible or implied lighting sources. Again, it's neither possible nor
desirable to use the lighting angles and positions that might be found
in a home. Instead, key lights might be placed to strike the subject
from the same general angle to the camera as the visible or implied
source. There might be key light from more than one general direction,
casting shadows representing several sources. Lighting angles from the
vertical, however, shouldn't be modified, since lowering key lights
will cause unacceptable shadows on backgrounds (or subjects) and
extremely steep angles will create dark shadows in eye sockets, as well
as long nose and chin shadows. Where the implied lighting source gives
off little or no light itself, the most distracting shadow of all is
that of the implied source cast on the background by the key light.
When this happens it's painfully obvious that the light in the picture
is not a practical source of illumination.
As a rule, it's better not to use visible implied light sources, since
it's difficult to protect the camera from them without destroying the
intended effect. Even an extremely low-wattage bulb in a table lamp
will exceed the contrast range a camera can accommodate, since it's a
source for direct, rather than reflected, light. Such apparently
innocent light sources as candles and lanterns give off more light than
many cameras can handle. The resulting effect is anything but
"natural." If some means of screening the camera from direct light from
an on-camera source can be found and if the appearance of the source is
reasonable natural, the effect of such implied lighting can be very
effective.
It's possible to suggest a light source through the use of distinctive
shadows. Special focused spot lights can be used to project patterns
onto the set. The pattern of a window might be used to suggest sunlight
streaming into a room, for example. With low light CCD cameras, even
normal slide projectors can be used to throw suggestive shadows.
Regardless of the light sources you use, the concepts of key, back, and
fill lighting are important to making your subjects as attractive and
dynamic as possible. Often in the real world you have to place the
camera and subject in such a way that existing light does this job for
you. In some circumstances (such as office-style fluorescent lighting)
there may be no alternative to bringing in additional lights for
modeling purposes. It's not important whether you use existing light or
normal tungsten lights or quartz-halogen television lights. The
relationship between the subject and the key light and the relationship
between key, back, and fill light sources is important to creating
effective images on tape.
Lighting
Lighting Instruments
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