Types of light sources
VIDEO AND FILM LIGHT SOURCES
Lighting fixtures come in all shapes and sizes. The design of a fixture, bulb, lens, reflector and accessories determines the nature of the beam and provides some methods of controlling it. A fixture’s beam characteristics (such as brightness, focusability, evenness, punch, softness, size, shape, color) dictate its function in the lighting arsenal. Each type of fixture has specific advantages in certain applications, and there are tricks to using each.
The first thing to understand about the lighting fixtures is the type of light source it employs. The principal sources used in film lighting are the tungsten incandescent bulb, the daylight-balanced arc lamp, fluorescents, and the new released LED technology.
The first group takes its name from the tungsten filament made incandescent by the electric current. In older kinds of bulbs this tungsten filament slowly evaporates and deposits itself on the inside of the bulb, thus darkening the globe and lowering the color temperature over the life of the bulb. Large 10K lamps contained a cleaning agent that had to be manually swished around inside of the globe between uses to clean off the tungsten blackening. To circumvent these process quartz halogen bulbs were designed. A tungsten halogen bulb is a type of incandescent bulb that contains special regenerative elements to prevent deposits of tungsten from blackening the sides of the globe. The regenerative elements carry the evaporated tungsten back to the filament, where it is reused, thereby increasing the life of the bulb. For the regenerative process, called the halogen cycle, to occur, a high temperature (at least 250°C) must be maintained inside the globe; and for this reason, tungsten halogen globes tend to be compact and made of quartz, which can withstand the high temperature. Quartz bulbs not only retain steady color temperature but show other advantages such as longer life, smaller size and quieter operation.
The fixtures using the tungsten source can be categorized by their housing. In this way we distinguish between lights furnished with lens (like Cinelight Fresnel) and the so called the open-ended or open reflector lights (exemplified through the Cinelight Reheads or Blondies). A lamp that may be viewed as a hybrid of these two types is the sealed beam globe with the lens constituting its integral part (these are the tungsten PAR lights).
Now, in the TV and Film industry there are four categories of lights depending on the type of lamp used: tungsten lights, HMI lights, fluorescent lights, LED lights.