LIGHTING

Television Lighting Television is a means of changing patterns of light into electrical signals for storage or transmission and then recreating those patterns on a screen. In order to do this well, the television camera must be presented with properly illuminated scenes. The three important considerations are overall level, contrast range, and color temperature.

Level Lighting

levels for television are generally set by adjusting the incident light, or the light striking the subject. The unit of measure for incident light is the foot candle, which is the amount of light produced by a standard candle at a distance of one foot. Lighting measurements are made using an incident light meter, which has a white plastic cover over the sensing element and a logarithmic scale calibrated in foot candles. To measure the useful incident light for television, the meter is held near the subject and pointed toward the camera.

Contrast

Contrast refers to the difference in brightness from the darkest parts of a scene to the brightest. Useful contrast for television is determined by the amplitude of the video signal. The NTSC standard calls for a "peak to peak" amplitude of one volt at 75 ohms impedance. Only seven tenths of a volt is used for the luminance, or black and white part of the signal. If there's too little contrast many receivers will produce a flat, grayish picture. If there's too much contrast, details in the brightest and darkest parts of the picture will be lost and the picture will look too harsh.

Color Temperature

The third consideration is color temperature. Every source of light has a characteristic color. This color is related to its "temperature." Lower color temperatures tend to be red or orange while higher temperatures tend to be green or blue. Color temperatures are measured in degrees Kelvin. Some example

Color Temperature

Temperature Source Color

1950 Candlelight Orange

2870 Normal Incandescent Orange

3200 Most Photo or TV Lights Orange

3400 Some Photo Lamps Orange

3500-4000 Fluorescent Lamps Green

5500 Midday Sunlight Blue

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

Back Light

The back light is placed directly behind the subject, in line with the camera. It, too, is set at a fortyfive degree angle from vertical. The back light is spotted down and aimed at the subject's neck. It isthen flooded until it has about the same intensity as the key light. The back light should be adjusted toproduce a crisp but subtle border around the subject. People with blonde (or missing) hair require lessintensity. People with very dark hair require more. When the back light is still too bright in the fullflood 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 theintensity of the key and back lights. It should also be softer, producing no harsh shadows. Often abroad, scoop, or soft light is used instead of a spotlight to provide fill. Fill lights are also frequentlyscrimmed 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

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 isnecessary 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

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

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.

 

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.

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.

Backlighting

Backlighting 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, backlighting doesn't completely eliminate "fill" light on the subject and may not therefore provide sufficient anonymity for the subject.