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7–30 • Keying Synergy Series Operation Guide (v18)
Chroma Key Lighting Tips
Achieving a good, clean chroma key is often considered one of the most challenging exercises in a
studio. There are several elements that contribute to an effective chroma key including, lighting,
distance of the talent from the background, type of background used, and the type of camera used.
However, lighting is often considered the most important. Here are a few lighting hints which you
may find helpful when setting up your chroma key.
Lighting the Background
• There are several different kinds of lights typically used to light chroma key
backgrounds. The most common are, cyclorama lights, soft lights, scoops, florescent
lights, HMIs, and umbrella lights.
For the most part, the one thing that they all have in common is the fact that they are
“fill” type lights, as opposed to “key” lights. These lights provide an even, diffused, flat
light, which is critical in lighting chroma key backgrounds.
• For best results, lights are usually hung in an even pattern from a grid above the
background but space requirements may dictate the lights be positioned on stands beside
the background. If side lighting is used, ensure the lights are positioned at equal
distances from the background being lit, in order to achieve balance.
• The number of lights used to light a background is directly related to the size of the
background surface. Therefore, a larger, longer surface requires more lights than a
smaller one. But whatever size of surface you are lighting, the most important point to
remember is the background should be lit as evenly as possible to avoid “hot spots” in
the chroma key.
• When lighting the background, experienced lighting directors will first of all eyeball the
background for hot spots, adjusting and readjusting the lights, but then check their work
using either a waveform monitor or a photographer’s light meter. Waveform monitors
are most useful since they display a graphical representation of the video level and any
small variation in light level is immediately apparent. On the other hand, a light meter in
the hands of an experienced professional can achieve the same results.
• Generally speaking, best chroma key results are achieved with an even level of light on
the background in the area of 60 – 75 IRE on a waveform monitor. However, conditions
specific to your application may dictate a value outside of that range.
• If you only have access to key type lights, you can simulate the effect of fill lights by
bouncing a key light off of a reflector and then on to the chroma key background. Also,
you can use diffused glass, gels, or scrims to soften the light from a key light. If you use
any of these methods it’s important to note that you will lose a significant amount of the
original light intensity. Therefore, it takes more lights to reach the optimum IRE level
required for a good chroma key.
Lighting the Foreground (Talent)
• You can maximize the quality of your chroma key if you separate the foreground (talent)
from the background by 6 – 8 feet. This enables you to light the foreground and the
background separately, thus reducing or avoiding “spill” and/or shadows.
Separation also allows you more flexibility in how you light your talent. You may still
choose to use a flat lighting technique, but with separation, the option exists to light your
talent using a more dramatic 3-light, “Rembrandt style of lighting”, typically used in
other lighting applications. This style is characterized by 3 lights – a key, a fill, and a
back light.