Background
lighting
A background light is used to illuminate the background
area of a set. The background
light will also provide separation between the subject and the background. Many
lighting setups follow Three-point
lighting or 4-point lighting setup. 4 Point
lighting is the same as 3 Point lighting with the added addition of a
background light. In 4 Point Lighting, the background light is placed last and
is usually placed directly behind the subject and pointed at the background. By
adding a background light to a set, filmmakers can add a sense of depth to
shots.
In film, the background light is usually
of lower intensity. More than one light could be used to light uniformly a
background or alternatively to highlight points of interest.
In video and television,
the background light is usually of similar intensity to the key light because
video cameras are less capable of handling high-contrast ratios. In order to
provide much needed separation between subject and background, the background
light will have a color filter,
blue for example, which will make the foreground pop up.
Black
Lighting
A black light, also referred to as a UV-A light, Wood's lamp, or simply ultraviolet light, is a lamp that emits long wave (UV-A) ultraviolet light and not much visible light. The lamp has a violet filter material,
either on the bulb or in a separate glass filter in the lamp housing, which
blocks most visible light and allows through UV, so the lamp has a dim violet glow when
operating. Black light bulbs
which have this filter have a lighting industry designation that includes the
letters "BLB".
A
second type of bulb which is also called a black light produces ultraviolet but
does not have the filter material, so it produces more visible light and has a
blue color when operating. These are made for use in "bug zapper"
insect traps and are identified by the industry designation "BL".
Black
light sources may be specially designed fluorescent
lamps, mercury vapor lamps, light-emitting diodes, or incandescent lamps. In medicine, forensics, and some other
scientific fields, such a light source is referred to as a Wood's lamp (named
after Robert Williams Wood).
Although
many other types of lamp emit ultraviolet light with visible light, black
lights are essential when UV-A light without visible light is needed,
particularly in observing fluorescence,
the colored glow that many substances emit when exposed to UV. Black lights are
employed for decorative and artistic lighting effects, diagnostic and
therapeutic uses in medicine, the detection of substances tagged with fluorescent dyes, rock-hunting, the detection of counterfeit money, the curing of
plastic resins and attracting insects. Strong sources of long-wave ultraviolet
light are used in tanning beds. Although the low power UV-A emitted by
black lights is not a hazard to skin or eyes and can be viewed without
protection, powerful ultraviolet sources present dangers and require personal protective equipment such as goggles and gloves.