light source used in addition to the main and fill lights to enhance
separation and dimension in the image. Examples of accent
lights include: hair light, kicker light (a.k.a. skim, rim or edge),
and veil light.
Angle of Incidence =
Angle of Reflection:
oft-quoted law of optics that describes how rays of light reflect
off of a plane (flat) surface. This principle lies at the
heart of the understanding of the behavior of directly reflected
light source used to light the background. The background
light may provide a general wash of light over the background to
control tone or may be more localized to create a sense of
separation between the subject and background.
a background that is dyed
or painted with a specific green or blue color. Image
processing software designed for Chroma-Key recognizes the specific
color and then manipulates these green or blue areas, usually by
dropping in another background. You can see Chroma-Key in
action on TV-based weather reports. The weather maps behind
the broadcaster are generally drop-ins. Using Chroma-Key,
portrait photographers can provide the customer with a huge
selection of backgrounds, but color fidelity at the composite
boundaries can make its use problematic.
Fill or Fill Light:
a lighting source used to lighten
(fill in) shadow areas created, in general, by the main light.
How fill lighting is provided varies greatly. Some
photographers prefer to use fill in a "global" sense, providing a
general wash of light that covers the entire set and sets a
"foundation" of light onto which other lighting is added.
Others, prefer to fill "locally", using reflector panels to bounce
light from others sources--usually the main light--into specific
pockets of shadow.
an offsetting (and
finessing) of a hot-centered-lighting source such that only the
"sweet" light surrounding the center is used to light the object.
Feathering is usually used with hot-centered parabolics and silvered
umbrellas, but feathering can be applied whenever a source has a
an opaque object, often in
the form of a flag-shaped frame covered with black fabric,
used to block light.
Grids are used to limit
the spread of light. Grids used directly on the flash
reflector are typically constructed from a fine honeycomb of
aluminum which is coated in matte black. Grids for larger
fixtures, such as softboxes, are more commonly made of cloth formed
into a grid of squares.
object, generally placed between the subject or surroundings and a
light source. Gobos may be entirely opaque (flag) or may
pass light selectively to create patterns (cucoloris).
describes the tonal key of
images that are predominately composed of lighter tones and white.
In addition, high key images are often characterized by softer than
normal contrast and an ethereal nature. High key is typically used
for portraits of women and children.
Inverse Square Law:
a law that states that intensity
decreases as the inverse square of the distance. Many common
lighting sources fall off at approximately this rate. A
bare-bulb flash, for instance, follows this law quite closely.
For more on the math and geometry of light fall-off, click here.
device that measures the quantity of light that either falls on the
meter (incident reading) or reflects off of a subject (reflective
reading). Some light meters measure only continuous light,
while others are capable of measuring both flash and continuous
a ratio that expresses either the
difference in the light levels illuminating the highlight and shadow
areas, or the difference in the actual light output of two sources.
Since these two ratios are not necessarily the same, confusion and
argumentation often rule when lighting ratios are involved. If
you'd like to learn more about the calculation of ratios, click
describes the tonal key of images
that are composed of predominately darker tones and black. In
addition, low key images are often characterized by higher than
normal contrast and a serious or somber mood. Low key is used
for all subject types.
Main Light (Key
a main source of illumination and
the light source that typically defines the contours of the subject.
In facial portraiture, the main light is responsible for lighting
the "mask" of the face and creating the shadow areas neighboring
such features as the nose, chin, and cheeks. The main light is
typically the strongest light in a multi-light setup, but not
a self contained studio
flash unit. A monolight combines the pack and head components
into one device. Monolights tend to be highly adjustable and
may be preferable for those who require different and precise output
from each lighting fixture.
thin but durable fabric that is typically dyed and/or painted.
Most muslins are made of cotton, but some, such as those from Botero,
are entirely synthetic.
Pack and Head System:
flash system consisting of a single power source (Pack) and several
flash heads that plug into the pack. The head generally
contains a flash tube, a modeling light, some minor circuitry, and
often a fan. Flash heads are generally light in weight and
either contain a reflector or can be fitted with a reflector or
other light-control device. The pack contains the control
circuitry, the power supply that converts the mains power to the
higher voltages used in strobes, and the capacitors that store the
charge distributed to the heads.
a bowl (paraboloid) shaped
reflector used to intercept and redirect the light from the
flashtube. The light quality of parabolic reflectors
varies widely. Most parabolic reflectors produce a light with
a "hotter" center, which is best feathered.
panel or screen used to reduce or soften the light. Scrims
made of black mesh reduce light level without appreciably affecting
light quality, while white cloth scrims both diffuse and attenuate
a heavyweight background paper,
usually on a cardboard core, that comes in a variety of sizes,
colors and shades.
box-like structure that is fitted around the lighting units
flashtube and which directs the light through a diffuser on the box
side opposite the flashtube. Like umbrellas, softboxes turn a
small source of light into a larger, softer source. Softboxes,
which usually have five opaque faces, and in some instances a
recessed diffuser, can provide better control of stray light than
collapsible reflector that can be used in several configurations to
enlarge, soften and broaden a light source. Photographic
umbrellas are constructed much like the handheld umbrellas we use to
protect ourselves from the rain, but with materials
appropriate to lighting, and with no handle. Umbrellas are
often overlooked in favor of the more controllable and expensive
softbox. You will find umbrellas in various forms, including:
shoot-through, silver, gold, zebra, and satin.
measure of energy that is also known as a Joule. The
Watt-Second rating of a flash unit is a measure of the maximum
electrical energy drawn by the unit and is closely related to the
amount of energy available for discharge into the flashtube.
The light output of the flash unit is rather loosely tied to the
Watt-second rating. Equally rated units from different
manufacturers can deliver significantly different light output.
Things such as, reflector coverage, flashtube treatments, and cable
extensions can have a major impact on light output.