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f/
Abbreviation for F/Stop.
Fahrenheit
A graduated scale used to measure temperature, with ice being 32°
and steam being 212°.
Fall-Off
A term used to describe the illuminated area just outside of the
field. (This term may also refer to the illumination in this area.)
Light from a point source, falls off inversely to the square of
the distance. Move the light from 10' away to 20' away, and you
have 1/4 of the intensity; 40', 1/16th. Diffused lights fall-off
even faster than point sources.
Tip: To minimize fall-off within a scene, use hard-lights
as far away as practical.
fc
Abbreviation for Foot-candle.
Feed Through (Feed Thru)
A wiring system employed in some electrical equipment and
luminaires such that the line side leads or flush mount connector(s)
for a first item branch into two circuits internally. One circuit
provides the electrical supply to the item itself, and the second
circuit exits the unit by means of a set of load side leads or another
flush mount connector(s). This allows for a second item to be electrically
connected to the first. A plurality of items may be connected in
this way, usually luminaires such as striplights.
Female
A term applied to a connector that contains the holes and/or slots
for receiving the pins, prongs, blades and/or tabs of a male connector.
The female connector should always be attached to the line side
of a circuit.
Field Angle
The angle of the vertex of a cone-shaped beam where the perimeter
of the base is defined by where the intensity is 10% of the maximum
intensity.
Field Diameter
The diameter of the base of a cone-shaped beam where the perimeter
of the base is defined by where the intensity is 10% of the maximum
intensity.
Filament
The wire inside an incandescent lamp envelope that glows and emits
light when heated, i.e. when electricity passes through it.
Fill
To create the illumination needed to reduce shadows in an area or
on a subject.
Fill Light
Used from the side opposite that of the key light, this light softens
the shadows created by the key and evens out the lighting ratio.
Filter
A term that refers to color media, diffusion material, or neutral
density filter.
Filter Frame
See the definition for Color Frame.
Finger
A small, narrow, rectangular scrim, diffuser, reflector, or gobo,
placed close to a luminaire, used for dimming, softening, bounce
lighting, and casting shadows, respectively. They are usually 2"
to 6" in length, and 12" to 14" in width.
FL
A lamp designation that means “flood”.
Flag (Filter, Gobo)
An opaque panel, usually made of fabric, placed into the beam of
a luminaire to block a portion of the beam or the whole beam. It
can also hide lights in the dark recesses of a scene. They are usually
square or slightly rectangular in shape, ranging from 10" to
48" in length, and 12" to 48" in width. Which term
you use depends upon the device’s size and what part of the
country you are in.
Flat Light
See the definition for Diffuse Light. All light is characterless,
textureless and shallow-shadowed, when the source is close to the
camera. Soft light is, by its nature, flatter than Hard Light, but
even a soft source, above or to the subject’s side, is not
flat. Example: Vermeer Lighting.
Flicker
The strobing of some luminaires that cannot be visually detected
because of the frequency of its output voltage, but can adversely
affect the way motion picture film records light.
Flicker-Free
A term used to describe electronic ballast’s that electronically
alter the electrical frequency that causes flicker.
Flood
- The position
of a moveable lamp, lens or pair of lenses on a spotlight that
produces the widest field angle.
- To direct
a large amount of light on a relatively large area.
Flood
Light
A luminaire consisting of a rectangular, lamp and sometimes a single
lens, used to direct a large amount of light on a relatively large
area.
Floppy Flag
A large flag that is designed to fold in half and function as a
cutter or smaller flag.
Fluorescence
The property of certain materials to absorb radiation of certain
wavelengths, usually ultraviolet, and re-emit the radiation as light.
Foamcore
A polystyrene, styrofoam material used as a substrate for some reflector
boards, effective because of its lightweight and ease of mounting
via reflector forks.
Focus
To aim and adjust a luminaire to give the beam its desired size
(spot or flood), edge (soft or hard), field (even or peak), and/or
shape (round, patterned or cut).
Focus Lens
A movable lens in a multi-lens optical system that adjusts the focus
of a luminaire.
Follow Spot
A narrow-beam focusing instrument that is manually operated and
usually comprises a powerful light source, an iris, shutters, a
color changer, and perhaps other features. It is usually operated
from an adjustable stand and is used to follow performer(s) on a
stage with its beam, surrounding the performer(s) in a large pool
of light.
Foot-candle (fc)
A non-metric unit of measurement for Illumination, i.e.
1 lumen per square foot.
Framing Projector
A spotlight that has framing shutters.
Framing Shutters
Thin, movable, heat-resistant metal plates that are introduced into
a beam such that a portion(s) of the beam is blocked off, i.e. framed,
affecting the beam pattern, usually forming a sharp edge in the
beam. They are used in various types of luminaires, but extensively
in ellipsoidal spotlights, usually 4 (top, bottom, right and left),
and follow spots, usually 2 (top and bottom), always situated internally,
and usually at the aperture. Framing shutters generally can be independently
adjusted, but those used in follow spots usually move simultaneously
with a single control mechanism.
French Flag
A small metal flag, usually used for shading.
Fresnel
An abridged version of Fresnel Spotlight.
Fresnel Lens
Named for its inventor, French physicist Augustin J. Fresnel, and
developed around d 1800 for lighthouses, this is a flat lens consisting
of concentric rings on one side that are segments of the spherical
portion of a plano-convex lens. The other side is flat, i.e. plano.
It controls light in the same manner as a plano-convex lens. Many
luminaires employing this type of lens have a stippled pattern on
the flat side of the lens to diffuse and therefore smooth out the
beam.
Fresnel Spotlight
A spotlight employing a single fresnel lens that produces a soft-edged
beam and usually provided with a spherical reflector and a means
to adjust the focus from spot to flood.
F/Stop
A rating often applied to scrims used in the film and video industries
on their ability to dim light. This rating is directly elated to
a camera’s ability to allow for the admittance of light.
Full Scrim
A metal scrim whose screen occupies the complete frame.
Fuse
An electrical device designed to open a circuit automatically on
a predetermined overcurrent. Some fuses automatically close when
the overcurrent no longer exists, but most do not.
Fused
Quartz
A relatively pure, high-temperature glass used to manufacture lamp
envelopes. It has a melting point point of approximately 1650°
C.
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