G – a certificate issued by the MPAA indicating that a film is suitable for all ages. see also PG.

GN – abbreviation for Guide Number.

GPI – General Purpose Interface.  1.  A parallel interconnection scheme that allows remote control of certain functions of a device. One wire per function. May also refer to any nonspecific interface between equipment. Usually refers to a serial connection (RS232 or RS422 format) between computer modules.  2.  mostly used in broadcast and post production equipment. Some of these external devices do not have the ability to be directly controlled by the editor. In this case the GPI signal is used to synchronously “start” this equipment at the same time.

GPU acceleration – ability of video player software to take advantage of the Graphics Processing Unit hardware in a computer, mobile device or game machine to make the decoding and display of digital video faster and more reliable.

GRB (green, red & blue; RGB) – the three primary colors used in video processing, often referring to the three unencoded outputs of a color camera. The sequence of GBR indicates the mechanical sequence of the connectors in the SMPTE standard. All electronic colors are additive colors, and hence the “primaries” red, green, and blue are used. Electronic colors, which include all screens and therefore all computer graphics and animations, are artificial. Natural colors, such as paint, fruit, and so on, are subtractive colors, and the three primary colors are red, yellow, and blue.  see also my Image Glossary for more about color; and also my PhotoList; and more urls with info. about color are on JKU One, in Art, the first Category.

GUI –  an acronym for Graphical User Interface”. An interactive graphic displayed on a screen, being a means of operating software.

gaffer – chief lighting technician. The head of the electrical department, responsible for the design and execution of the lighting plan for a production. Early films used mostly natural light, which stagehands controlled with large tent cloths using long poles called gaffs (stagehands were often beached sailors or longshoremen, and a gaff is a type of boom on a sailing ship). In 16th century english, the term “gaffer” denoted a man who was the head of any organized group of laborers.

gaffer’s tape – a strong adhesive tape used in film and television production.

gain –  1. any increase or decrease in strength of an electrical signal. Gain, degree of amplification, the difference between the signal level at the input of a device and the level at the output, a measure of how much a signal is amplified,  is measured in terms of decibels.  Electronic signal amplification.  2.  The ability of a projection screen to concentrate light.

gamma – 1. measurement of the contrast of an image, representing the slope of the straight-line portion of the characteristic curve. Gamma correction controls the overall brightness of an image. Images which are not properly corrected can look either bleached out, or too dark. Trying to reproduce colors accurately also requires some knowledge of gamma. If an image is under or over gamma corrected, this also affects the color balance. Over correction (in addition to making mid-tones too light) shifts colors towards neutral grey, while under correction (in addition to making mid-tones too dark) shifts colors towards the display primaries. If your computer sends the monitor a message that a certain pixel should have intensity equal to x, it will actually display a pixel which has intensity equal to x  2.5 Because the range of voltages sent to the monitor is between 0 and 1, this means that the intensity value displayed will be less than what you wanted it to be. (0.5 2.5 = 0.177 for example). Monitors, then, are said to have a gamma of 2.5.   2.  When expressing a color in RGB, what we are trying to specify is the amount of light which will be emitted from each phosphor, as a fraction of full power. What we are actually specifying is however the voltage which will be applied to each electron gun. The two are not linearly related, because the amount of light emitted is proportional to the beam power rather than the voltage. The beam power is the product of voltage and current, and current turns out to be roughly proportional to the grid voltage to the power 1.5. Thus, the light emitted is proportional to the voltage to the power 2.5 or so. The actual value of the exponent, called gamma, varies somewhat and the power law is only an an approximate model of the real situation, albeit a good one. An additional optical effect caused by viewing images against a dim surround is that the effective gamma value is somewhat reduced, from a theoretical 2.5 to around 2.2

gamut – the boundary of a color space. Colors outside the “gamut” of a specific color space are considered “illegal” for that color even though they may be well within the “gamut” of a different color space.  2. a color gamut in photography and image-editing is the definitive, complete range of colors which can be accurately represented in a particular situation, such as within a certain color space; or the complete range of colors in an image.

gate – 1. a signal used to trigger the passage of other signals through a circuit. 2. a digital logic device whose output state depends on the states of the logic signals presented to its inputs.  3. an audio processor that allows signals to pass only above a certain setting or threshold.  4. the aperture assembly at which the film is exposed in a camera, printer or projector.  5. In synthesizers,  a clock pulse signal often used to externally control or trigger the note-on, note-off state of an analog synth, to drive the rate of an the LFO or envelope, to start/stop a sequencer or arpeggiator and more. CV and Gate work together to provide the MIDI-like ability to control synths. Gate input and/or output jacks may also be labeled Trig, V-Trig, or S-Trig.

gate array – a set of basic logic gates contained in one integrated circuit.

gauge – 1. a characteristic of film that refers to the width, perforations, and other physical features. Gauges range from 5mm to 105mm, although 8mm, 16mm and 35mm are most common. 2. a thickness or diameter of a wire.

gaussian blur – In image-editing software like , gaussian blur blurs a digital image according to a radius value (e.g. 5 pixels) that you select in advance.  It blurs incrementally across the object to be blurred, providing a pleasant and realistic softening effect. See also blurs.

gel – a thin, tinted plastic-like sheet placed over a light to change the color of the projected light. “Cleaning the gels” is a practical joke usually given as a job to an inexperienced crew member.

gelatin – a nearly transparent substance, obtained by boiling animal tissue in water, used as 1. the medium for suspending light-sensitive silver halide crystals on photographic film, and 2. in the manufacture of gelatin filters.

gelatin filter – 1. also known as “gelatin slide” and “gel,” a thin sheet of translucent colored gelatin for placing over lights to obtain lighting effects, and in the manufacture of photographic filters for lenses. A light filter consisting of a gelatin sheet in which is light-absorbing pigment or dye.  Gels are available in a wide variety of colors and densities. 2. generic term used in reference to any colored translucent material (color media) that is used to color a light, whether the material is made from gelatin, glass or plastic.

gen-lock (genlock) – 1. to phase-lock the timing of one piece of equipment to another.  2. to lock the synchronization signals of multiple devices to a single source; the condition which exists when the sync generators of multiple devices are locked to a single source.  3. to reference a signal generator to a signal normally external to and separate from the system controlled by the signal generator. The purpose is to bring a system, such as a studio, into proper timing with an external source, such as a live remote camera, so that special effects as wipes, keys, and dissolves can be done using the external source in combination with internal sources.  4. the process of locking both the sync & burst of one signal to the burst & sync of another signal thus making the two signals synchronous.

gen-lockable master – a main facility sync pulse generator that is capable of locking to an outside source of video.

general MIDI –  a set of requirements for midi devices aimed at ensuring consistent playback performance on all instruments bearing the gm logo. Some of the requirements include 24-voice polyphony and a standardized group (and location) of sounds. For example, patch #17 will always be a drawbar organ sound on all general MIDI instruments. MIDI device standards that guarantee regular playback on gm instruments.

generator –  genny, Genny Operator. A mechanical engine which produces electricity from fuel (usually diesel). Frequently used for location shooting, either due to the unavailability or insufficient quantities of electricity locally available.

ghost image – in time (or long) exposure photography, an object that is only partially recorded on the film and therefore has a translucent, ghost-like appearance. Ghosting also occurs when using electronic flash at a slow shutter speed, and a second image is captured on the film by ambient light. Some people also refer to “flare” as a ghost image.

ghosting – 1. artifacts typically caused by signal leakage (crosstalk) between the two ‘eyes’. A secondary ‘ghost’ image can be seen. There are several possible causes that can introduce the problem during acquisition, post production and display. One reason can be high contrast levels between an object and its background.  2. A shadowy or weak image in the received picture, offset either to the right or to the left of the primary image. It is the result of transmission conditions where secondary signals are created and received earlier or later than the primary signal caused by a reflected RF signal. Echo is a wave which has been reflected at one or more points in the transmission medium,  resulting from reflection of transmitted broadcast signals during off air recording (signal reflection from tall physical structures like skyscrapers or airplanes) and signal routing problems with continuing video signals. Echoes may be leading or lagging the primary signal, and appear in the picture monitor as reflections or double images commonly known as ghosts. The terms “ghost” or “ghosting” is also used to describe and effect called image lag, an artifact of certain types of video tube cameras. Ghosting has been noted as being similar to ‘print through’, the condition where low frequency signals on one tape winding imprint themselves on the immediate adjacent tape windings. It is most noticeable on audio recordings where a ghost of a recording can be heard slightly before playback of the actual recording. If the artifact is recorded into the media, it cannot be fixed.

gigabyte – a digital storage capacity equivalent to one-billion bytes, for british readers, one thousand million bytes.

gigantism – confusing visual cues in a stereoscopic scene that can make an object appear to be the ‘wrong’ size i.e. the impression of strangely enlarged size of objects. This is due to the choice of interocular distance relative to the focal length of the camera lenses, e.g. shooting with an interocular distance much less than adult human eyesight can make a figure appear to be a giant. see: miniaturization, interocular.

giraffe – a mechanically extendable and manipulated boom microphone.

glass bead screen – screen covered with tiny glass beads, each of which provides a spherically reflective surface.

glide – a function, also called portamento,in which the pitch slides smoothly from one note to the next instead of jumping over the intervening pitches.  The pitch slides evenly from note to note.

global – 1. pertaining to or governing all of the operations of an instrument. 2. oversees the working of a musical instrument.

global illumination – 3D animation. Family of algorithms wich, when determining the light falling on a surface, take into account not only the light which has taken a path directly from a light source (direct illumination), but also light which has undergone reflection from other surfaces (indirect illumination).

glossy paper – shiny-surfaced, photo-sensitive paper used in making photographic prints.

gobo – a light-blocking device that falls under the general category of “grip equipment.” Generally used in a studio to prevent illumination from a studio light striking a portion of a scene. A “gobo” can be a simple piece of opaque cardboard or  a sophisticated material in a specific shape, often a rectangle or square. “Barn doors” are gobos.  2. A patterned template used in lighting to create a pattern or texture in a scene. Placed between the light and the subject, a gobo can add mood, dimension, or the illusion of motion.

golden hour – the time an hour or less before the sun goes down and around fifteen minutes after the sun has set. Sunlight is usually warmer and more complimentary to skin tones at this time, and the angle of the light can provide depth to portraits and landscape photography. This quality of light is also sometimes referred to as “photographer’s light.”

golden mean – also referred to as the “golden section” and the “gold mean”, the golden mean mathematically defines a rectangle of specific proportions. This rectangle, called the “golden rectangle,” frames objects in pleasing proportions. (see rule of thirds for more information.) See Jae Kamel’s Dictionary for more about the Golden Mean and Ratio, and JKU One under Natural Mathematics.

golden rectangle – also known as the golden ratio, golden mean, golden section or divine proportion. A rectangle of specific mathematical proportions that are closely approximated in the shape of a 35 mm film’s frame or the viewframe of a digital camera. The rectangle defined by the golden mean.

go motion – also go-motion. A form of animation similar to stop motion, but which incorporates motion blur. ordinary stop motion cannot produce motion blur as motion only occurs between frames.  Robotic models that are moved during the exposure of each frame produce motion blur, and thus are more realistic. Pioneered by Industrial Light and Magic for Dragonslayer.

goof – a take of a scene not used in a movie, usually because of an on-camera mistake made by the cast or crew. Also see out-take.

gost – gost is a standardization system (1951–1986) developed by the All-Russian Scientific And Research Institute For Certification. (On March 19, 1992, VNIIS was reorganized as the Russian Research Institute for Certification. In July 2004, the Institute was incorporated under a name “The Russian Research Institute for Certification”, JSC (VNIIS, JSC). ) Its coding system for film speeds, although similar to the ISO system, uses different numbers.  It was an arithmetic film speed scale defined in GOST 2817-45 and GOST 2817-50. Used since October 1951, replacing Hurter & Driffield (H&D, Cyrillic: ХиД) numbers, which had been used since 1928. GOST 2817-50 was similar to the ASA standard, having been based on a speed point at a density 0.2 above base plus fog, as opposed to the ASA’s 0.1. GOST markings are only found on pre-1987 photographic equipment (film, cameras, lightmeters, etc.) of Soviet Union manufacture. On 1 January 1987, the GOST scale was realigned to the ISO scale with GOST 10691-84; and then on 1 January 1992, GOST 10691.6–88.

Gouraud shader – 3D animation. Calculates surface by linearly interpolating between normals of adjacent polygons. Gouraud shader is a simplified version of lambert shader and is especially suitable for real-time rendering on graphics hardware, i.e hardware rendering. Developed by Henri Gouraud in 1971.

gradation – 1.  an image’s tonal contrast range.  2. the range of light and dark tones in a subject that a film is capable of showing (i.e. how a film reproduces contrast). 3.  the gradual changing of one tint or shade to another by very small degrees.

gradated filter – also called a “graduated” filter. a filter that is not uniformly dense, but that gradually changes its density across the filter’s field. A gradated neutral density filter is clear from one edge to approximately the middle of the filter, then gradually increases in density towards the opposite edge. Colored gradated filters gradually change color density across the filter’s field.

gradated gray filter – another name for a gradated neutral density filter.

gradated neutral density filter – see definition in “gradated filter” above.

grade – a system of classifying the contrast of photographic papers used in making black and white prints, ranging from 0 (soft) to 5 (hard).

graduated filter – see gradated filter above.

grain – minute crystals of silver halides in the light-sensitive emulsion of film that react when exposed to light, turning black, are called “grains.” (see graininess of film.)

graininess – graininess occurs when clumps of individual grains are large and irregularly spaced out in the negative. they are visible to the naked eye in the finished print, particularly enlargements, as sand-like particles. when this occurs, the picture appears “grainy.”  This is due to the grouping together, or “clumping” of the individual silver grains, which are by themselves far too small to be perceived under normal viewing conditions.  2. Graininess in digital images is caused by “noise,” which usually appears in shadow areas and is generally unwanted and unattractive.

grain reduction –  Digital algorithms used to reduce the amount of undesirable grain in a sequence of images. Examples: noise reducers; smoothers; blurs.

granularity – non-uniformity in a photographic image that can be measured with a densitometer, or with a microdensitometer.  2. A negative or film that shows a granulated structure, usually used to describe the degree of granularity that is visible.

graphics adaptors – commonly referred to as a ‘video card’, which outputs computer signals.

graphic editing –  a method of editing parameter values using graphic representations (for example, of envelope shapes) displayed on a computer screen or lcd. Revising visuals exhibited on a monitor or screen.

graphics pipeline – the series of functions, in logical order, that must be performed to compute and display computer graphics.

gray card – also known as the “kodak neutral test card,” a gray card is an 8″ x 10″ (20 cm by 25.5 cm) card, about 1/8″ thick, that is uniformly gray on one side. the gray side reflects precisely 18% of the white light that strikes it (corresponding to the calibration of a reflected-light meter). It is uniformly white on the other side, which reflects 90% of the light. Visually it appears neutral, or a middle gray halfway between black and white.  The gray card is a simple but effective aid in determining proper exposure.

gray filter – another name for a neutral density filter, or nd filter.

grayscale – the range of monochromatic shades from white to black in an image. A grayscale image contains no color – only values, shades of gray, or tones (256 of them) – and is more commonly known as a black and white (b&w) image. Note that a color image also contains grayscale information. In art, black and white are values, not colors. However, only pure black or pure white are values.  When the black, white, or gray has any color in it at all, any hue, it is a color then, and not a value. See also my Image Glossary for more information about colors; and Julie Eclair’s PhotoList; and also JKU One, in the Art Category.  There are links there to important color sites.  2. a chart with varying shades of gray which is photographed during production and used by the film processing lab to color correct film.

grayscale mode – 1. a camera setting used to capture digital black and white images. 2. an image’s mode may be changed from, say, RGB mode to grayscale mode, in an image-editing program by discarding the image’s color information, or by converting it to black-and-white.

green – one of the three “primary” color signals (red, green, and blue) produced by cameras and other video sources. More generally, an artificial, additive color produced electronically.

greensman – a member of the crew who procures, places, and maintains any vegetation on a set.

greenscreen – a newer technique similar to bluescreen, however utilizing a key green background. Research showed that substantially better results could be gained by filming on green instead of blue, as effects stock was more sensitive to separating key green from other (foreground) colors. See also chroma-keying.

greyscale – same as grayscale.

grip – In the usa, a grip is a skilled person responsible for the set up, adjustment and maintenance of production equipment on the set. Their typical duties involve camera movement, lighting refinement, and mechanical rigging. In the UK, grips work exclusively with equipment that the camera is mounted on, responsible for the transportation, maintenance and mounting of the camera. Contrast with swing gang, see also key grip.

grindhouse – a term used to describe movie theaters common in the u.s. from the 1950s onward, that specialized in showing, or “grinding out” as many b movies as they could fit into their schedules. The term is also used to describe the type of b-movies, commonly violent, exploitative, or just plain racy, that were shown in such theaters.

grooved recordings – the surface of the media is altered by creating grooves that when read by a stylus, or needle, reproduce sound. Grooved recordings may include cylinders, discs, and belts. Dependent on the type of grooved recording encountered, specific playback equipment and styli may be needed to playback correctly.

gross fog – The density of the base of the film plus the density of the fog in the emulsion. Also known as D-min and base + fog.

ground glass screen – flat sheet of glass in a camera treated so that it can be used for viewing and focusing an image, also known as the “viewing screen.”

grounding – the techniques and hardware that connect electronic equipment and wiring to a reference point.

guide number – a number which serves as a guide to proper exposure when using flash. also known as “flash factor.” The number is based on a flash unit’s light output and a digital camera’s iso sensitivity setting or a traditional camera’s film speed. When the guide number is divided by the flash-to-subject distance, the correct aperture for proper exposure is determined. Guide numbers may be quoted in meters or feet, according to which system is used for the measurement of distance.

guide rollers – any roller with flanges that is used to guide or restrict the position of motion picture film as it moves through a camera, projector, or printer.

guillotine splicer – device used for butt-splicing film with splicing tape.