Lighting: Overall System
Any TV lighting system has to provide the correct quantity of light on the subject (illumination) and, for colour television, must also provide light of the correct quality (colour temperature). To satisfy these needs it requires light fittings (luminaires), means of supporting them and a system for controlling the light output from each lamp.
How elaborate our facilities need to be will be influenced by:
● Camera sensitivity.
● Size of acting area.
● Height of lighting ceiling (lighting grid).
● Turnround time required between programmes.
If the initial design is for a simple lighting suspension but more flexible arrangements are likely to be needed at a later date, the ceiling and steelwork to meet the later requirements should, if possible, be put in at the time of building the studio. It is difficult and expensive to add these features later.
Camera sensitivity
The sensitivity of the camera channel determines the lighting level required: the subject illumination. It is usually quoted for a given signal/noise ratio in terms of subject illumination when operating the camera at a normal lens aperture. It should be noted that the use of any front-of-lens prompting device will need an increase in the required lighting level.
Size of acting area
In the small TV studio the whole of the available staging area is gradually used and our lighting set-up needs to accommodate several adjoining regions. The precise nature of the action in each changes for each programme and the lighting system must be flexible enough to cater for these different situations. If initially, for economy reasons, only part of the studio is being used, the lighting system can be restricted accordingly. This will cut costs but will make the system less adaptable.
Height of studio grid
The height of the studio has been discussed earlier (page 20). The maximum height of the luminaires above the studio floor is directly related to this and so also is the maximum lamp throw (lamp-to-subject distance). This factor coupled with camera sensitivity fixes the wattage of luminaires to be used.
Turnround time
How long it takes to modify a lighting set-up to suit a new production is largely determined by the suspension system, and is discussed on pages 92/ 94. Generally, the more flexible systems offer the quickest turnround.
| Studio lighting levels ( 1 lumen/m2 = 1 lux) | Power requirements (based on the total studio floor area) | ||
| 500-800 lumens/m2 | 250 watts/m2 | ||
| Add extra power to cater for cyclorama lighting | |||
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| Colour camera type | Typical studio lighting requirement | *Nominal lens aperture |
| 3 × 1 lead oxide vidicons | approx. 800 lux | f/2.8 |
| 3 × ⅔” lead oxide vidicons | 600–750 lux | f/2.0 |
| 3 × ⅔ ” format CCD | 200–500 lux | f/2.0 |
| 3 × ½ ” format CCD | approx. 300 lux | f/1.4 |
* For a given shot this lens aperture will maintain similar depths of field for the different format sizes.
† This will be close to the maximum lens aperture, so it may be more convenient to operate at f/2.0. This will enable the lens iris to be ‘opened-up’ as well as ‘stopped-down’ during vision control operations. Depth of field will increase, and sensitivity will halve, as a consequence.
Studio lighting requirements