Basic Techniques of Lighting for Video
By David Martin Jacques
Copyright © 2001 by David Jacques
To be Published in the February, 2002, issue of Church Production Magazine
As most large churches are now incorporating live video projection into their services and many broadcast their services to local and national affiliates, lighting designers must have at least a basic understanding of video lighting techniques to meet the challenges of this technology. This article will speak to the techniques of video lighting design from the simple parishioner with a camcorder, to broadcast quality design.
I have lit numerous broadcasts of live and taped events for local and national organizations. From designing the lighting systems for houses of worship that incorporate live and taped video, and lighting video productions for PBS, NBC, and A&E networks, I have discovered along the way some tricks of the trade to pass on to you.
The first question I ask when lighting a video production is: "How many cameras are you using and where will they be located?" This will tell me how many angles I have to be concerned with. Remember, the camera is the "moving eye" of the audience. Unlike the audience's static placement in the house, the camera is able to view the subject from any angle. Therefore, you must be sure that the subject is lit correctly from multiple points of view.
When lighting for the camera some very important points must be understood. First, it is crucial to realize that the camera is not as sensitive as your eye. Video equipment "sees" intensity and color differently from you and I. In addition, since video is a two-dimensional medium, people and objects not lit correctly tend to look flat and blend into the background. These concepts may be basic, but are critical when designing lighting for video.
Although advances in video cameras are continually developing, it is still a fact that most moderately priced video equipment will not see objects clearly in very dim light. This is due to the video equipments' limited dynamic range. This is the term used to describe the range between the dimmest light the camera can see without excessive noise, and the brightest light before the object blooms in a mass of white light. As video equipment is equipped with irises, you can always close down the iris to reduce the amount of light entering the lens. However, if you push the gain or sensitivity to capture a dim subject, electronic noise is created which reduces the clarity of the image. (The latest digital cameras have extremely sensitive lenses and low-light capability. However, your margin for error is reduced greatly at such low lighting levels.)
The lighting director must provide a reasonable amount of consistent light when illuminating the stage for video. This means that the lighting intensity for the entire area that the subject will be walking through should not deviate more than 10%. If the lighting intensity deviates much more than that, then dark "holes" will be exaggerated on video as the person walks in and out of these areas. A good digital light meter is an invaluable tool for this test.
Although many cameras have auto-irises to compensate for darker areas, if the iris has to open for a dimmer foreground, then the background will get brighter too. This inconsistency is certainly not desirable, especially when dissolving from camera to camera. In large multi-camera productions, large variables in lighting intensities will drive the video engineer crazy as the cameras must be continually adjusted, or shaded, for these inconsistencies.
It is a good idea to keep the background areas illuminated within 30% of the foreground intensity. This is so the camera's irises don't close too much from a bright foreground object, making the background too dark. Great care should be given to lighting foreground to background. Good foreground to background lighting also helps add depth.
Another consideration regarding lighting intensity levels is when you use multiple follow-spots. Extreme care must be taken when two subjects in separate follow-spots move near each other and the lights overlap. The lighting intensity will usually double when this happens and the irises on the cameras must quickly close to compensate--rendering the background darker. The correct technique is to have one follow-spot fade out as they cross to keep a consistent lighting level. This is why good spot operators are worth their weight in gold when lighting for video.
Remember, the camera can only see what the lighting designer illuminates. The camera may not be able to see dimly lit objects that can otherwise be seen by the human eye. If you wish the camera to see the audience, then the audience must be sufficiently lit. The same idea applies for architectural walls, ceilings, aisles, and entrances.
Regarding cueing, it is wise to avoid blackouts and wide variables of lighting
intensities. A lighting blackout leaves the television screen in total darkness--not
nearly as effective as when you experience a lighting blackout as a live audience
member. Sudden increases in intensities may cause the image to bloom or become
over-saturated with light. If you have many cameras that are moving around,
it may be impossible for the camera operator to focus on the subject if there
is no light available. When shooting a live show I always call "lights
up" cues a few seconds early to allow the camera operator a chance to focus
before that camera is cut to.
As video is basically a two-dimensional medium, objects lit just from the front tend to look "flat" and blend into the background. It is imperative that the lighting director help create the sense of a three-dimensional world. This is partially accomplished through the use of backlight. This is trickier than it sounds as the correct intensity, color, and angle of light is critical in achieving this effect. I suggest that the intensity of the backlight is at least 50% brighter than the foreground. It is also important to choose a color that will flatter the hair, skin, and clothes of the people being lit. Usually a pale color correction of clear light is used for this effect. This is usually accomplished by adding a color correction filter to the backlight. Or, if using automated lighting, you can "dial-in" the color remotely to highlight the clothes and hair of the subject.
Regarding angle, the key is to use an angle that highlights the rim of the hair and the shoulders. If the angle is too high, then unattractive shadows of the nose, chin, and cheeks appear. If the angle is too low, then the three-dimensional effect is reduced. Another good idea is to make sure that the color of the background offers a good contrast to the foreground. This is why you usually see a lot of green plants behind pastors. Green is a good contrasting color to human skin. Avoid colors that incorporate flesh tones as this causes subjects to blend in with the background.
Another important consideration is how video "sees" color. White balancing is the process in which the camera is adjusted for it's relative white color. This is a complex subject that certainly deserves it's own article. However, let's suffice it to say that the lighting director must decide what color the relative white will be and make sure that all the cameras are balanced to it. This is accomplished by focusing a light with the relative white color on a perfectly white card that reflects all wavelengths of color. The cameras are focused on this card and the electronics are adjusted to treat this color as white. All other colors that the camera "sees" are then based on this relative white color.
Color can also be a challenge when mixing arc and incandescent sources. It is important to understand that the color of an incandescent light will change as it is dimmed down (amber drift). This is not true when using arc sources in most automated lights as the dimming process is mechanical and does not cause the color to shift--another reason why I use arc fixtures for many of my video productions.
Most incandescent lamps have a color temperature of 3200K, while arc sources have a color temperature of 5600K (hence the blue tint to its "clear" color). Most automated lighting fixtures have color correction filters that will balance its source color to 3200K to closely match the incandescent sources in your light plot. You could also color balance your cameras to 5600K, and color correct your incandescent sources closer to that temperature if you want your saturated automated lighting colors to read correctly on video. I use this technique often on large automated lighting productions that also use supplemental incandescent sources (for audience lighting, fill lighting, etc.)
Speaking of audience lighting, I recently worked on a church (Riverbend Church, Austin, Texas) that has a large arched window upstage of the pulpit that allows a huge amount of natural daylight to flood into the sanctuary. Due to this bold architectural design, it was necessary to color balance all the interior stage and audience lighting to 5600K to better match the daylight. As the camera angle from upstage past the pastor to the audience is a common one used in worship productions, the audience house-lights were matched to this natural daylight color. We designed metal halide arc house-light fixtures with a color temperature of 5600K to be used for the daytime services. As the church also broadcasts their evening services, a second system of incandescent house lights is used. If we did not do this, the video would have the pastor in one color of light and the color of the congregation would look totally different.
Finally, when lighting a production for video figure on spending most of your time in the control room or video truck watching how the lighting looks though the monitors. If there is no control room, then at least look though the camera. This is the only way you can efficiently and accurately do your job. Remember, when lighting for video, the eye of the camera is the eye that counts.