D-1 – also D1. Digital video tape format using the CCIR 601 standard to record 4:2:2 component video on 19mm tape. Formerly the highest quality video tape format generally available. The first digital video tape format, hence D-1. A non-compressed digital video recording format that uses data conforming to the ITU-R BT.601-2 standard. D-1 records on high-end 19mm (3/4″) tape.
D-2 – Also D2. An 8-bit non-compressed composite digital videotape recording format in which the composite video signal is digitized by sampling it at the rate of four times the frequency of subcarrier (4fsc). The 4fsc frequency in NTSC is 14.3 MHz and 17.7 MHz in PAL. Conforms to SMPTE 244M; uses four (4) 20-bit audio channels. D-2 records on high-end 19mm (3/4″) tape and a cassette similar to D-1. The second digital video tape format, hence D2.
D-3 – also D3. An unofficial term for a composite digital videotape recording format invented by Panasonic. Digital video tape format using 4fsc composite signals like D2, but recorded on 12.5 mm (1/2-inch) tape. The third digital video tape format. A non-compressed digital recording format that uses data conforming to SMPTE 244M and four (4) 20-bit audio channels. D-3 records on high-end 3/4″ tape.
D-4 – Doesn’t exist. The number 4 is considered unlucky in Japan.
D-5 – 1. Digital video tape format using CCIR 601, 4:2:2 video. Uses the same cassette as D3. 2. a non-compressed, 10-bit, 270 Mbit/ second, component or composite digital video recording format. D-5 records on high-end 3/4″ magnetic tape.
D-7 – DVC-Pro.
D-9 – Digital-S (D-9). Digital-S was introduced as a professional upgrade to VHS. When the Digital-S standard was officially accepted by the SMPTE, (the Society of Motion Picture and Television Engineers) it then became the D-9 format, which then found its way into professional applications. D-9 had a pre-read function that incorporated the simultaneous use of separate record and playback heads. This made it possible to see the recorded signal a split-second after it was recorded.
D-connector – A type of connector that has a trapezoidal shell resembling a “D”.
DA – (see distribution amplifier) – An acronym for “Distribution Amplifier”. A device used to multiply a video signal so that the signal stays constant throughout a number of devices.
DA-88 – A Tascam-brand eight-track digital audio tape machine using the 8 mm video format.
D/A converter – also DAC. 1. A device that converts digital signals to analog signals. 2. The part of a sound card which plays back a numerical representation of audio as an analog, real world sound like a voice or guitar.
DAT – An acronym for Digital Audio Tape. A consumer digital audio recording & playback system with a signal quality surpassing that of the Compact Disc (CD).
dB – deciBel. 1. A unit used to compare the relative levels of electrical signals on a logarithmic scale. 2. A measure of voltage, current, or power gain equal to l/10 of a Bel. Given by the equations 20 log Vout/Vin, 20 log Iout/In, or 10 log Pout/Pin.
dBm – A measure of power relative to 1 mW. 0 dBm equals 1 mW.
dBSPL – a measure of sound pressure level measured in dynes per centimeter squared. Its reference, 0 dBSPL equals 0.0002 dynes/cm2. dBSPL is used as a measure of acoustical sound pressure levels, and is a 20log function.
DCC – Dynamic Contrast Control. Restores lost detail when shooting against bright backgrounds.
DCDM – DCDM is an acronym for Digital Cinema Distribution Master, Digital content that conforms to specifications set by the Digital Cinema Intiatives (DCI). The DCDM is a set of digital files that include images, audio, subtitles and other auxiliary data. The DCDM is made using the original finished picture-data from the DI process – normally 10-bit DPX files. To create the DCDM the data is encoded into 12 or 16-bit Tiff files for picture and 24-bit WAV files for audio. The DCDM provides the uncompressed master elements that enable the creation of the Digital Cinema Package (DCP).
D-cinema – Digital Cinema. It encompasses digital distribution and projection of digital cinematic material.
DC offset – The amount that the dc component of the signal has shifted from its correct level: an offsetting of a signal from zero. A signal with DC Offset would appear in the waveform view to be not centered on the 0.0 horizontal line. DC Offset results in reduced headroom and can cause clicks at the start and end or distortion after running effects. It can be corrected by normalization.
DCP – An abbreviation for “Digital Cinema Package”. A DCP is a collection of digital files used to store, organize and convey Digital Cinema image, audio and data streams. These include MXF, XML and JPEG2000 files. SMPTE standards are used to conform the various vendors, producers and distributors.
DCO – Digitally Controlled Oscillator. An analog oscillating circuit controlled and monitored by a digital microchip. This offers a very stable, accurate, self tuning analog sound in a synth and is less likely to overheat or drift out of tune.
DCT (Discrete Cosine Transform) – see also DFT and FFT. The DFT/FFT are excellent for convolution, and useful for frequency-domain analysis of sampled analog signals. So why did someone invent a new transform, the DCT? For image compression, we would like energy compaction; we would like a transform that reduces the signals of interest to a small number of nonzero coefficients. Image compression is often done in blocks. Suppose we select a small block from some natural image. The DFT of the block gives us the values of the discrete Fourier series of the periodic extension of that signal. Suppose the periodic extension has a discontinuity at the block boundaries. Then the DFT coefficients will decay slowly, just like the FT of a square wave (discontinuous) decay as 1/k, whereas those of a triangle wave decay as 1/k 2 . So any discontinuities in an image, include at the boundary of a block, lead to poor energy compaction of the coefficients. As an additional drawback of the DFT, if the image is real, then its coefficients are complex. All other things being equal, when developing image compression methods one would usually prefer real valued quantities over complex values if the original image is real. To overcome these drawbacks of the DFT, discrete cosine transform (DCT) uses the trick of taking the image (block) and forming a symmetrized version of it before computing a DFT. This symmetrization has the effect of eliminating discontinuities at the block edges, and yielding real coefficients. Interestingly though, the DCT is derived via the DFT. So Fourier analysis is still the fundamental tool, even for this new transform.
DDR – An acronym for “Digital Disk Recorder”. Systems that record video or audio programs on one or more hard drives. They are mostly used in broadcast or radio broadcasting when editing or recording is required. The benefit of these systems: they offer immediate access to the material that was recorded before, without requiring pre-roll/post-roll or expensive maintenance of tape heads. 2. A digital video recording device based on high speed computer disk drives. Commonly used as a means to get video into and out from computers and for editing.
DFT – Discrete Fourier Transform. There are many ways that the Discrete Fourier Transform (DFT) arises in practice but generally one somehow arrives at a periodic sequence numbers. These numbers may arise, for example, as discretely sampled values of an analog function sampled over some period window and then extended periodically. They may also arise as a discrete set of values from the measurements in an experiment. Once again we would assume that they are extended periodically. In any case, the DFT of the sequence is a new periodic sequence and is related to the original sequence via a DFT inversion transform similar to the Inverse Fourier Transform. The DFT turns out to be very useful in spectral analysis of both Fourier series and Fourier transforms. As the name implies, the Discrete Fourier Transform (DFT) is purely discrete: discrete-time data sets are converted into a discrete-frequency representation. This is in contrast to the DTFT that uses discrete time, but converts to continuous frequency. Since the resulting frequency information is discrete in nature, it is very common for computers to use DFT (Discrete Fourier Transform) calculations when frequency information is needed.
DFTC – Drop-Frame Timecode. SMPTE timecode created to match run-time or clock-time, exactly. Two frames of timecode are dropped every minute except every tenth minute. Broadcasters require masters to be delivered with DFTC.
DI – An abbreviation for “Digital Intermediate”. DI is the process of digitizing a film (e.g. by color correction, inserting transitions, conversioning, conforming, etc…) before it is distributed into movie theaters.
D-ILA – Digital Direct Drive Image Light Amplification projectors.
DIN connector – Deutsche Industrie-Norm. A connector that follows the German tandards system that expressed a film speed rating by a number followed by a degree symbol ( ° ) for electronic connections. The DIN system has been replaced by the more universal ISO system.
DIN Sync – Also known as Sync24, DIN sync is a form of tempo and start/stop synchronization used by old Roland drum machines and synthesizers. Most notably, the TR-606, TR-808, TR-909, TB-303, and MC-202. A DIN Sync cable looks just like a MIDI cable, but there is a difference. MIDI cables are wired differently and will not work with these older machines. To get a DIN Sync cable these days, you can find them at any electronics store as a generic 5 pin DIN cable. No rewiring is necessary.
DIP switch – 1. Dual in-line package switch. 2. A PC module mounted switch package of dual inline style, typically mounting from two to eight switches and used in such functions as mode assignment and address selection.
DivX – High compression, high quality, low bitrate. Variation of MPEG-4. Good results, usually found in .avis combined with .mp3 or .ac3 sound.
D-Log E – Density vs. the log of Exposure. The graph made by plotting the density of a film sample against the log of the exposure that made that density. Also known as D-Log H, H and D, and characteristic curve. D-Log H (H for exposure) is the technically correct term.
D Log H Curve – The curve showing the relation between the logarithm of the exposure and the resultant density on processed film. Also called the characteristic curve.
DLP – Digital Light Processing(c) by Texas Instruments. A projection system that has technology based on the Digital Micromirror Device (DMD). It uses thousands of microscopic mirrors on a chip focused through an optical system to display images on screen.
D-Max – See Maximum Density.
D-Min – See Minimum Density.
dpi – dots per inch. 1. printer – a measure of print resolution, that is, the number of dots of ink per linear inch of an image. the greater the number of dots, the higher the image’s resolution. 2. scanner – a scanner’s maximum resolution is measured in dots per inch. when the number is high, the scanner can scan more data from an original image, increasing the scanner’s output quality. 3. images – when the spatial resolution of pixels in an image is altered, a digital image can be made larger or smaller. This is usually referred to as ppi (pixels per inch).
DPOF – Digital Print Order Format. A set of universal standards permitting you to specify print options directly from a digital camera.
DPX file – Digital Picture Exchange. The most common file format used in digital post-production. The DPX format is an ANSI and SMPTE standard. The format provides a great deal of flexibility because it is easy to share between workstations, equipment, and facilities. This file format can be found in digital film work and is considered an ANSI/SMPTE 268M standard. DPX files can store image data and additional metadata in their file headers.
DSLR – Digital Single Lens Reflex camera. DSLR cameras with high-definition video were introduced early in the 21st century. Although they still have the handling and usage deficiencies of other multipurpose devices, HDSLR video offers the shallow depth-of-field and interchangeable lenses lacking in consumer camcorders. Professional video cameras with these capabilities are more expensive than the most expensive video-capable DSLR. In video applications where the DSLR’s operational deficiencies can be mitigated, DSLRs such as the Canon 5D Mark II provide depth-of-field and optical-perspective control.
DSP – Digital Signal Processor; also Processing. A special processor circuit that is designed to perform complex operations on audio or video waveforms. This specialization permits sophisticated sounds to be produced rapidly and efficiently. This architecture may be compared with video and graphic processor circuits that have been used to accelerate and improve video output. DSP is used in sound cards, or audio equipment to create sound fields which are electronic or digitally synthesized acoustical environments for audio enhancement, and to create time delays and for precise steering of multi-channel Dolby Pro Logic information. Broadly speaking, all changes in sound that are produced within a digital audio device, other than changes caused by simple cutting and pasting of sections of a waveform, are created through DSP. A digital reverb is a typical DSP device.
dts – Digital Theatre Systems file extension. Surround sound audio stream similar to AC3 but supposedly less compressed, leading to greater fidelity. Used in some cinemas and found on many commercial DVDs. There are many others, notably Qualcomm Purevoice, QDesign Music, ulaw, etc…
DTV – Digital Television; a signal transmitted digitally.
DV – A video tape format designed primarily for the consumer market that records a 4:1:1 standard definition signal with a 5:1 compression ratio for a total bit-rate of 25Mb/second. DV cassettes come in two sizes — Standard & Mini. Low compression. Found on video form DV camcorders, used in iMovie.
DVC – Digital Video Cassette. A digital tape recording format using approximately 5:1 compression to produce near-Betacam quality on a very small cassette. Originated as a consumer product, but being used professionally as exemplified by Panasonic-s variation DVC-Pro, and Sony-s variation DVCam.
DVCPro HD – A High-Definition format developed by Panasonic. It uses ¼-inch wide tape stock and records 22:11:11 8-bit HD video. The DVCProHD was an upgraded version of DVCPro. However, the tape speed was increased to four-times that of DVCPro.
DVD – An acronym for Digital Versatile Disc or Digital Video Disc. Similar to a CD in physical structure, it is the same size as a compact disk (CD) but has seven times the data capacity, up to 17 Gbytes. There are a number of different types of DVD. At the time of writing these include DVD-R, DVD-Rom, DVD-RAM, DVD+RW, DVD-R/W. DVD is not a suitable archival format for video mainly because it uses a lossy form of compression – MPEG2. It is also a format that is likely to see rapid changes in technology and therefore the risk of speedy obsolescence is high. DVDs are made up of a reflective aluminium layer, a polycarbonate substrate, a dye layer and a clear lacquer. The aluminum layer is highly susceptible to pollution and the lacquer layer does not sufficiently protect the aluminum layer to prevent oxidation. Where the DVD is double-sided the two sides are bonded using an adhesive. The adhesive have not been subjected to accelerated aging tests by the manufacturers and there is little data on their life expectancy. A DVD is the same diameter as a CD (120cm) but cannot be read by the same equipment. DVD and CD both record data by encoding it as tiny pits in tracks that correspond to the zeros and ones of binary digits. The pits are read by laser and played back. DVD is able to store more data by making the pits smaller and the tracks closer together and employing the compression system MPEG II. 2. Many artists use DVD-R as an exhibition format and this has replaced laser disc as a popular display format for many museums and galleries. However, because of the way the data is encoded frame-accurate control cannot be achieved by referencing the picture content as it can with laser disc. Where external control is needed for display it is important to be clear of any specific requirements of the control system before having the disc(s) made. DVD-R discs were introduced in 1997 with the capacity of 3.95 GB and a track pitch of 0.8 microns that later, by reducing the track pitch to 0.74 microns, this was increased to 4.7GB. There are two types of DVD-R discs; “General” and “Authoring”. This has caused some compatibility issues as the lasers in the players for these discs need to be angled differently. Professional DVD players will have both lasers, however if you are using a domestic model it is important to check which discs your player is compatible with. This is also true for all other types of disc as there is unfortunately a lack of compatibility between playback equipment at this time. DVD is a rapidly developing technology and there is a continued push to increase the amount of data that can be stored on a disc.
DVE – Digital Video Effects. A -black box- which digitally manipulates the video to create special effects, for example, the ADO (Ampex Digital Optics) system. Common DVE effects include inverting the picture, shrinking it, moving it around within the frame of another picture, spinning it, and a great many more.
DVI – An acronym for “Digital Visual Interface”. It is a video standard interface that will maximize the visual quality of digital display devices (e.g. computer displays, LCD panels, digital projectors and more). It is especially suited for uncompressed digital video data. 2. a connection method from a source (typically a computer) and a display device that can allow for direct digital transfer of data. The digital signal is limited to 5 meters.
DVI-D – one of two common multi-pin connectors available for DVI signals. The DVI-D carries no analog video information, only digital. The digital signal is limited to 5 meters.
DVI-I – one of two common multi-pin connectors available for DVI signals. The DVI-I adds analog video to the connection, permitting greater distances than the digital limit of 5 meters.
DVR – Digital Video Recorder. 1. A DVR is basically a VCR that uses a hard drive, SD card, or flash-drive instead of video tapes. It can be used to record, save, and play back television programs. Unlike a VCR, however, a DVR can also pause live TV by recording the current show in real time. The user can choose to fast forward (often during commercials) to return to live television. Most satellite and cable TV companies offer a DVR as an option with their digital television packages. Since cable boxes already provide program listings through some kind of TV guide interface, most DVRs allow users to use the guide to schedule recordings. For example, a user can use the remote to search through the guide’s program listings for the current week and select the shows he would like to record. In many instances a DVR will replace your cable box and you can watch without a cable or satellite subscription. With many DVRs you have the option of acquiring a CableCARD from a cable provider and accessing digital channels by inserting the card into a slot on the DVR. The majority of DVRs have internal hard drives that allow you to record shows directly onto the device. Several manufacturers have different DVR types on the market, including TiVo, Motorola, RCA and Scientific Atlanta. Some companies, such as ReplayTV, are targeting PC users, offering software packages that turn your computer into a DVR. In addition, Sony, Panasonic and Toshiba produce DVD recorders that include a hard drive, allowing them to act as DVRs. Some cable companies like Time Warner, Comcast and Cox offer cable television packages that include a DVR. DVRs conveniently save shows in an list that the user can access at any time. Since the shows are stored on DVR’s hard drive, there is no need to rewind or fast forward to play a certain show, like a VCR requires. Most have recording options which let you set the DVR to record your favorite shows whenever there is a new episode and skip all the rest,so you will never forget to set it and your hard drive won’t get bogged down with shows you’ve already seen. While the majority of DVRs have plenty of internal storage space, they often have eSATA ports that let you connect to an external hard drive to expand your recording capacity even more. Many DVRs have streaming apps allowing you to access channels over the air or through unscrambled digital signals instead of paying monthly cable fees. Some DVRs have streaming options and give you access to both digital and analog (over-the-air) channels. It wasn’t that long ago that the thought of having the ability to manipulate live TV by pausing, rewinding, fast forwarding and even slowing it down seemed almost ludicrous. But virtually all DVRs can now do exactly that. You can skip over commercials. A USB port can facilitate expanded storage and connect to a mouse or a computer. An HDMI port allows you to connect to a computer or TV via an HDMI cable to access online content and assure top-quality digital sound and video. Some DVRs also have analog connections to access over-the-air content. If you don’t subscribe to cable,make sure the unit you buy can pull free channels from over-the-air broadcasts and unscrambled digital signals. If you want to build a large HD library of recorded movies and full seasons of TV shows, you should find a DVR with terabytes of storage space. Many of the latest models also have built-in Wi-Fi, and also let you access live TV on your mobile devices.
2. With new recording technology our complete hidden camera systems eliminate the need for additional equipment. This is a completely self contained camera and DVR recording system. With Mpeg4, 30fps, Motion detection, and Time & Date stamp, they record directly to SD cards for storage and easy playback on your PC. Capable of being built into many different styles of covert camera. This complete hidden camera system is the only hidden camera you will ever need to have. These hidden cameras move into the future eliminating the need for separate VCRs and DVRs. See the Hidden Camera section for more information .
D-sub connector – a generic name for D-shaped serial connectors used in data communications.
dailies – 1. Film dailies are the first one light work print made from an original negative usually printed immediately after processing the negative so that action, lighting and rough color can be checked before the next days shoot begins. Same applies to video dailies. 2. Picture and sound work-prints of a day’s shooting; usually an untimed one-light print made without regard to color-balance. Referred to as “rushes” in England. They are produced so that so that the action can be checked and the best takes can be selected; usually shown before the next day’s shooting begins.
darkcloth – Material used to cover the photographer’s head and camera to block surrounding light in order to better view the image on the camera’s ground glass viewing screen.
darkroom – A room in which total darkness is achievable, permitting light-sensitive materials such as film to be handled without fear of their exposure to light.
darkslide – An opaque sheet that is slid in place over the front of a sheet film holder to protect the film from exposure to light.
data CD – Data CDs contain data intended to be read directly by a computer. The data may include audio and any other types of file such as images and documents. Most standalone CD players will not play data CDs, but some DVD players will. Including compressed audio files on a data CD can greatly increase the playing time compared to audio CDs.
data compression – A technique that provides for the transmission or storage, without noticeable information loss, of fewer data bits than were originally used when the data was created. See also Julie Eclair’s Image Glossary .
data dump— 1. A packet of memory contents being transmitted from place to place (usually in the form of MIDI system-exclusive data) or stored to a RAM card; and more generally, 2. transferring data between locations or to a memory card.
daughter-board – a tiny circuit board that when affixed to a bigger board possesses additional aptitudes.
daylight – Light consisting of a natural combination of sunlight and skylight (approximately 5500 degrees K). Technical note: all the light we see from the surface of the earth, with our eyes, during the day, is “skylight”. We see no sunlight per se at that time.
daylight film – Color film designed to render correct color balance when exposed in normal daylight.
daylight setting – A camera’s white balance setting that results in a scene’s accurate color representation when in bright sunlight at noon.
decamired – A filter system for colour conversion, also known as photometric, used by some continental European manufacturers. Unlike the arbitrary and fairly random Wratten series the decamired system relies on easily calculated mathematical relationships. Colour temperatures are measured in decamireds (mired being a microreciprocal degree). Filters are either red (R, KR and CR) or blue (B, KB and CB). The filters are additive so stacking a CR 3 and a CR 6 filter will give a total decamired value of 9.
decibel – (dB) Unit measured on logarithmic scale used to measure audio levels. decibel (dB): A unit of measure of loudness used to represent audio transmission levels, gains or losses. It describes the smallest perceptible change in audio level. A comparison of two measurements or values. Abbreviated dB, it is one-tenth of a Bel (a unit of measurement named for Alexander Graham Bell). See dB, above.
decoder – A device used to recover component signals from a composite (encoded) source.
decompression -When expanding a compressed file back into its original form it is uncompressed (or decompressed).
dedicated flash – An electronic flash unit that integrates automatically with a specific camera’s exposure meter and exposure controls, permitting simplified, fully-automatic use of the flash. A dedicated flash is designed to work with a particular model, brand or type of camera.
definition – Sharpness of an image (as seen by the clarity of detail) formed by an optical system.
deflection coil – a uniform winding of wire used to electromagnetically direct an electron beam to draw an image on a cathode ray tube (CRT).
defragmentation – Storing and deleting data on a storage medium such as a hard disk will cause in time a fragmentation of data on the storage. At that point the information is no longer stored as a large block in one place but scattered all over the storage. Though one will hardly experience this as a problem when working with a computer normally, when dealing with digital video it is of special importance: Then the data on the storage should be optimally aligned to be more suited for real-time operations. To achieve this you have to apply a defragmentation at regular intervals to the storage which will physically align the data properly on the storage. For this DVS developed a special defragmenter that even observes video clips consisting of
individual image files: The files belonging to clips will be aligned in blocks, thus truly facilitating real-time processes.
delay – 1. The time required for a signal to pass through a device or conductor. 2. An audio signal processing device or circuit used to retard the speed of transmission on one or more audio signals or frequencies.
demagnetization – A process that erodes audio-visual signals or data encoded on magnetic tape. This degradation is a natural phenomenon whose speed varies with the type and condition of the tape.
demodulator – 1. electronic device that removes information from a modulated signal. 2. A circuit that demodulates or decodes the desired signal from amplitude and/or frequency modulation present on a carrier wave.
demultiplexer (demux) – A device used to separate two or more signals that were previously combined by a compatible multiplexer and are transmitted over a single channel.
density – When referring to film, the density is the measure of the blackness of the image. Density is affected by both exposure and processing time.
densitometer – Instrument used to measure the optical density of an area in a processed image by transmittance (for films) or by reflectance (for photographic prints).
densitometry – Science of measuring the light-stopping characteristics of film or filters.
density – 1. Light-stopping characteristics of a film or a filter. The negative logarithm to the base ten of the transmittance (or reflectance) of a sample. 2. The relative opacity (blackness) of an area of a negative, a transparency or a print. The greater the density, the less light can be transmitted through it. (Sometimes density is also referred to as “Contrast.”)
densitometer – Instrument used to measure the optical density of part of a film negative or print.
depth channel – The distance of objects from the camera. Also known as Z-depth or Z-buffer channel.
depth cue – 3D animation. Atmospheric effects such as fog can be easily simulated by adding depth cue to the scene. Everything in the scene turns gradually into the fog color with the distance. Quick method of adding the feel of space to the scene.
depth grading – A post production process where negative and positive parallax convergence and divergence are adjusted. This is not only a creative tool used to place objects on the Z axis but also a way to ensure that stereoscopic content can be comfortably watched on the screen size it is intended for. For example, in a Post suite the Director may be viewing a film on a small projection screen but the final delivery format may be a large theatre or Imax. In practice the eyes have little ability to diverge (up to one degree is considered the rule of thumb) and this is especially a consideration in depth grading for very large screens with positive parallax images, where the distance between the left and right representations of an image may be very widely spaced. Sometimes the term Depth Budget is used to refer to the combined value of positive and negative parallax and expressed as a % of screen width. See: Parallax.
depth-of-field – The range of distance in a scene that appears to be in focus and will be reproduced as being acceptably sharp in an image. The area in front of a camera lens that is in focus from the closest item to the camera to the furthest away; a term used to describe the areas of a picture both in front and behind the main focus point which remains in focus. Its area of acceptable focus extends for a distance in front of and behind the point on which the lens is focused (i.e. the plane of focus). Depth of field depends on the lens opening (lens aperture), the focal length of the lens, and the distance from the lens to the subject.
depth of field preview button – Many cameras are equipped with a preview button that, when pressed and held in, stops the lens down to the pre-selected aperture, allowing you to see how much foreground or background are in focus.
depth of field scale – Markings on the barrel of a lens that show the depth of field for a particular aperture and a particular focus setting.
depth of focus – A zone of focus in the camera. If an image is focused on a ground glass screen in a camera, depth of focus makes it possible to move the screen slightly backward or forward and still have the image in acceptable focus.
detune — alters the pitch of one sound source as it relates to another.
developer – A solution for developing a film or photographic paper; for turning an exposed film’s or paper’s latent image into an image that can be seen. Chemical solution used to turn the latent image into a visible image on exposed film.
developing tank – A light-proof container used for processing exposed film.
development – The process of converting an exposed film’s latent image into one that is visible. It can be described as changing exposed film into a negative. Process of making a visible film image from the latent image produced during exposure.
device aspect ratio – The aspect ratio of the display device on which you view the rendered image. The device aspect ratio represents the image aspect ratio multiplied by the pixel aspect ratio.
diacetate – An early form of acetate film stock, diacetate is easily identifiable because it smells like camphor, or moth balls. Diacetate was used for non-theatrical and amateur films in the 1920s and 1930s. It was replaced by cellulose triacetate and other cellulose acetate film stocks.
diaphragm – A ring or plate with a hole in the center, the size of which controls the amount of light entering the camera. An adjustable diaphragm in a lens enlarges or reduces the size of the hole, or aperture, thereby permitting more or less light to pass through the lens to the film or digital sensor.
diascope – A viewer designed to enhance the viewing of autochromes.
definition – The clarity or distinctness with which detail of an image is rendered. Fidelity of reproduction of sound or image.
differential dc – Maximum dc voltage that can be applied between the differential inputs of an amplifier while maintaining linear operation.
differential gain – A change in subcarrier amplitude of a video signal caused by a change in luminance level of the signal. The resulting TV picture will show a change in color saturation caused by a simultaneous change in picture brightness.
differential looping input – A video input port that allows the signal to be looped through to another input.
diffraction – A phenomenon exhibited by a light’s wave front when passing the edge of an opaque object (one that does not allow light to pass through it). The light becomes modulated, causing a redistribution of the light’s energy within the wave front. You will see it at the edges of the object’s shadow, in the form of minute dark and light bands. The edges of the shadow have a fuzzy appearance. Think of ripples meeting a rock in a pond. They go around the rock in a new series of ripples that can be seen on the sides of the rock. Light waves behaving in a similar manner are said to be diffracted.
differential mode – refers to either noise or surge voltage disturbances occurring between the power hot and the neutral conductor. Most differential mode disturbances result from load switching within a building, with motor type loads being the biggest contributor.
diffuse RMS granularity – The objective measurement of grain.
diffuse surfaces – reflect (or scatter) light, and colour in many angles. This type of surface causes light and color to spread freely.
diffused light or diffuse lighting – Light that is scattered and spread out as opposed to specular light. Diffused light is softer than direct light, with shadows that are less sharply-defined (lower contrast).
diffuser – Material that diffuses light. A diffuser may be a translucent material or a rough-surfaced reflective material, both of which scatter light’s rays, thereby softening the light.
diffusing – 1. Moderating light so it is softened (diffused), generally either by reflecting it off a material that scatters the light or by placing a diffusing panel of translucent material between the light source and the subject. 2. Softening of detail in a print with a diffusion disk or other light-scattering material.
diffusion – the scattering or random redistribution of a sound wave from a surface. It occurs when surfaces are at least as long as the sound wavelengths, but not more than four times as long.
diffusion-condenser enlarger – An enlarger that has both a condenser system (for greater contrast) and a diffused light, producing less contrast than a condenser enlarger but more contrast and sharper detail than a diffusion enlarger (see below).
diffusion enlarger – An enlarger in which the light is diffused, and therefore spread more evenly as it strikes and passes through the negative, resulting in less sharpness of detail. Negative flaws (scratches, etc.) are de-emphasized with a diffusion enlarger.
digital – a method of transmitting information by discrete, non-continuous impulses, represented by a series of ones and zeros. 2. Circuitry in which data carrying signals are restricted to either of two voltage levels, corresponding to logic 1 or 0. 3. A circuit which has two stable states: high or low, on or off. 4. A system whereby a continuously variable (analog) signal is broken down and encoded into discrete binary bits that represent a mathematical model of the original signal. 5. In a digital synthesizer, sounds are stored as a binary code in some form of permanent or volatile memory, and are typically called a sample. This sampled string of binary digits is converted to an analog signal by a Digital to Audio Converter (DAC) inside the synth. A Digital synth has very clean, consistent and stable sounds, offers lots of memory, can be lightweight and can offer much more control and variability of the sounds it can generate.
digital-to-analog converter – an electronic device that converts digital signals into analog form.
digital betacam – 1. Digital video tape format using the CCIR 601 standard to record 4:2:2 component video in compressed form on 12.5mm (1/2-inch) tape. Digital Betacam was introduced by Sony in 1993 as a digital replacement for their very popular analog Betacam line introduced 20 years earlier. The format was based on a 1/2-inch tape format pioneered by companies such as Grundig and Phillips. In a similar way that users pushed Panasonic to improve DVCPRO by introducing DVCPRO 50, Digital Betacam users urged Sony to introduce a higher quality Betacam: Betacam SX. See also Digibeta, A digital video version of the professional-grade Beta video format.
digital clipping – When a digital signal exceeds 0 dBFS, which is the highest voltage level that an A/D converter can convert, samples are lost. Unlike analog distortion, where hot levels can produce a saturation effect, digital clipping is very unforgiving. Severe overs can produce what sounds like noise. However, any over in a digital system constitutes distortion, whether or not it is audible. Even subtle overs can be seen by zooming in to an audio waveform and viewing the peaks. If the peaks appear chopped off or truncated at the top of the wave, clipping has occurred. Can it be fixed? If digital clipping is heard or seen in the preservation master files, the source must be re-digitized. An individual over or two due to a transient sound, like a cough or a fist hitting the table, may be deemed acceptable if the transfer was otherwise at a reasonable level. Overs from a digital source can be repaired on production master files using a plug-in, such as Izotope’s Declipper. Preservation master files generated from an analog source will show digital overs if levels were not properly adjusted prior to digitization. These sources should be re-digitized at a lower level. Any digitized recording that shows consistent overs, meaning a signal constantly hitting 0 dB (digital zero), is by definition too hot.
digital intermediate – A project in its digital state between input and final output. The digital intermediate goes through many different processes such as digital retouching, digital color grading, integration of visual effects and titling. Therefore, the term “digital intermediate” refers to the digital data’s transitional nature-a state between the input stage and final delivery. digital intermediate. 2. A Digital Intermediate is the result of the process of shooting in High Definition or shooting on film followed by scanning to film quality data files, editing the project in High Definition and applying the creative process of color correction and color treatment to the completed master. This Digital Intermediate then becomes the master for video, DVD or for theatrical output by transferring this data master back to film.
digital master – Final digital version with all changes in the image processing stage applied. It is used to create all distribution formats, including film, digital cinema, HD, SD, and DVD.
digital paint – Software tools and techniques to fix imperfections in digital images.
digital recording – Process in which sound waves are recorded as digital bits. Digital recording produces high quality, true sound that doesn’t contain noise.
digital television (DTV) – The transmitting of a broadcast signal that consists of digital data.
digital video tape – Video tape format that stores image on tape as a binary code, allowing it to be moved through various digital devices with minimum loss of quality.
digitizing – 1. The act of taking analog video and/or audio and converting it to digital form. In 8-bit digital video there are 256 possible steps between maximum white and minimum black. 2. (To digitize) process of sampling and converting a continuously variable (analog) signal into discrete mathematical representation of that signal.
digital camera – also called a digicam. A camera that takes pictures without film, but instead records the image on an image sensor chip in a format that is readable by a computer.
digital manipulation – Altering a digital image using image-editing software.
digital zoom – Zoom effect in some digital cameras that is not true (optical) zoom, but is instead an enlargement of the information from the center of the CCD or CMOS (image sensor). It is literally a cropping of the image at the sensor to give the illusion of the use of a telephoto zoom lens. Although the camera’s software interpolates the image so that it has the same resolution as a normal (non-digitally zoomed) image, it is not as sharp as an image created with an optical zoom lens.
digitization – The process by which analog images are converted to a digital form.
dihedral maladjustment – a condition resulting from a miscalibration of the playback heads. It is similar to skew in that it is a timing error resulting in a “bending” of the video image, however, skew is displayed as a uniform bending in one direction (left or right), and dihedral maladjustment displays as a fanning or V-shaped distortion, generally at the top of the image. Proper calibration of video heads requires that they are positioned 180 degrees apart, resulting in a full helical scan of the tape from rotation to rotation. The head switch controls which head is active with each scan of the tape. If the heads are slightly out of 180 degree phase, recorded video fields will be read too early or too late, resulting in a distortion of the image. The v-shaped skewing occurs because of the toggled field position, with lines read too late, positioned to the right, and lines read too early, positioned to the left. Dihedral maladjustment can be recorded into a video image, or it can occur as a result of poorly calibrated record machine. It may be possible to eliminate the dihedral artifact with a TBC, or in cases where it is severe, the playback heads on a machine can be calibrated to mistime correctly for the recorded program.
diopter – 1. a unit of measure of the refractive power (strength or magnifying power) of a lens. A prescription for eyeglasses is normally written with numbers that represent diopters. Greater vision correction is needed as the diopter measurement increases. 2. In photography, the term is used with close-up lenses to indicate their magnification and focal length, and with corrections to the camera viewfinder’s lens when adjusting it to suit the user’s eyesight, enabling the photographer to focus an image on the ground glass without wearing his or her eyeglasses. Note that not all camera’s viewfinders can be adjusted to compensate for the photographer’s eyesight. When they can, the cameras are sometimes said to have a “diopter.”
direct current (DC) – electricity that maintains a steady flow and does not reverse direction, unlike alternating current (AC). Usually provided by batteries, AC to DC transformers, and power supplies.
DirectShow – The Microsoft DirectShow application programming interface (API) is an architecture for streaming media on Windows. With DirectShow a software developer can implement all kinds of video and audio play-out and capture solutions in a software application. Various applications such as Windows Media Player use DirectShow already to display the video or audio content of files.
direct sound – also known as near-field, it is sound that is not colored by room reflections.
director’s cut – A rough-cut created by the director once the editor’s cut is complete.
direct vision viewfinder – a camera’s viewfinder that is not through the lens, as in a viewfinder camera. The photographer looks through it directly at the scene while the image is captured through a separate lens.
disk mirror – A Disk Mirror is a complete copy of data that resides on one physical disk to another physical disk. It doubles the data storage requirement when implemented. Also known as “RAID Level 1”.
disk striping – Disk Striping is a technique used for spreading data over multiple disk drives. Disk striping speeds-up operations that retrieve data from disk storage.
dispersion – can be seen when a white light beam passes through a triangular prism. The different wavelengths of light refract at different angles, dispersing the light into its individual components.
displacement mapping – 3D animation. An alternative technique in contrast to bump mapping, normal mapping, and parallax mapping, that uses a heightmap to cause an effect where the actual geometric position of points over the textured surface are displaced along the surface normal according to the values stored into the texture.
display – 1. a viewing screen, like that of a computer’s monitor or a camera’s lcd screen. 2. to show or exhibit, as in a display of one or more images.
dissolve – 1. Effect where one scene gradually fades out as a second scene fades in. 2. A certain style of transition where one clip blends into the next. Most common are dissolve rates from a half-second to two seconds. 3. The gradual change from one picture to another, allowing the pictures to be superimposed during the transition. An optical or camera effect in which one scene gradually fades out at the same time that a second scene fades in. There is an apparent double exposure during the center portion of a dissolve sequence where the two scenes overlap.
distortion – Any undesirable alteration in an audio or video signal. 2. misrepresentation of proportions of objects or of their arrangement in a scene. the two main types of lens distortion are barrel distortion, in which the straight lines near the edges of the viewframe appear bowed outward from the center, like a barrel-shape,and pincushion distortion in which the same lines bend in towards the center. 3. Another type is tonal distortion, in which an image’s contrast, brightness or colors appear markedly different from those of the subject.
distribution amplifier (DA) – 1. A device used to replicate an input signal, typically providing 6 outputs, each of which is identical to the input. May also include delay and/or cable equalization capabilities. 2. an active device used to split one input into multiple outputs, while keeping each output isolated, and the signal level constant.
distributed sound – a sound system in multiple loudspeakers separated by distance and typically operates in a lower sound pressure level than a high pressure system. The loudspeakers are most often suspended over the heads of the listeners.
dithering (or color quantization) – 1. simulating colors or shades with a smaller, limited number of colors or shades, creating the illusion of “color depth” in images. 2. Half toning or dithering are the methods used to produce a smooth gradation of colour versus distinct bands of colour or moiré patterns, in a halftone image. It is also how modern inkjet printers work.
diverging light rays – light rays that diverge, that is, continue to recede from each other, spreading or drawing apart. The opposite is “converge”.
document camera – an imaging device used to create a video image of printed documents or three-dimensional objects.
dodging – blocking a portion of the light when printing a photograph or manipulating a digital image so that an area of the image will be made lighter.
dolby system – Trade name for an audio noise reduction system.
dolly – 1. A wheeled device attached to a tripod to allow smooth movement of a camera. Also a camera movement toward or away from the subject (dolly forward, dolly back). 2. Moving the camera along the line of sight, i.e close and far from the target. Term originally refers to the carriage under the camera stand, pushed on wheels along rails.
dome – used in all ranges of speaker drivers.
dominant object – the object in a photograph that is predominant, usually one that is given the most visual weight and often appearing in the foreground.
dot crawl – also chroma crawl. A composite video artifact, dot crawl occurs as a result of the multiplexing of luminance and chrominance information carried in the signal. Baseband NTSC signals carry these components as different frequencies, but when they are displayed together, the chroma information can be misinterpreted as luma. The result is the appearance of a moving line of beady dots. It is most apparent on horizontal borders between objects with high levels of saturation. Using a comb filter to process the video can reduce the distraction caused by dot crawl when migrating composite video sources, and the artifact may be eliminated through the use of s-video or component connections. However, if it is present in an original source transfer, it might be compounded in subsequent generations of composite video transfers. Dot crawl can be remedied by using an S-Video or component video output on the playback VTR, if available. If not, many TBCs have integrated comb filters which may help reduce dot crawl if engaged, though some purists may debate this approach.
double-exposure – exposing the same image frame twice. a typical double-exposure shows the same subject twice in the same image.
double system recording – 1. Synchronous sound recording separate from the camera. Typically magnetic with sync pulse. 2. Includes a film camera and a separate device, such as a DAT, for audio. For accuracy, the camera should be synced with the sound device and the frame rate should be a constant 24 frames per second. Sound is later transferred to magnetic film and synchronized with picture in postproduction.
down-conversion – The process of converting high-resolution video to lower-resolution video.
downrating – means to expose a film to more light than its iso rating indicates. some say downrating is also known as “pulling,” but it is only step one in the pulling process, which includes overexposing (downrating) to reduce its effective film speed and underdeveloping the film to compensate for the downrating.
downrezzing – Resizing a digital image to a smaller size, or to a lower resolution.
down-sampling – reducing the file size of an image by making the image smaller.
dragging the shutter – a technique that involves using flash with a long exposure (from a slow shutter speed) to also capture background objects that are in ambient light.
drift – When an element does not keep a steady pace during playback. Usually caused when there is no time-code to lock to or when the record machine power supply is faulty. It can also refer to a color-correction setting on a telecine which has changed over time due to light-tube burn.
driver – 1. A program interacting with a special kind of software or particular device. The driver has special knowledge of the device or particular software interface that programs using the driver do not have. 2. in audio, an individual speaker unit.
drop frames – Frames/image files that cannot be read from or written to a storage device during a real-time operation have to be dropped i.e. they will be omitted during a play-out or record. A drop can be caused by all kinds of reasons, for example, a fragmented video storage, where data is physically scattered over the hard disk so that it takes too long to read it in time.
drop frame mode – SMPTE time code runs at 30 frames/second, while the NTSC color television system runs at about 29.97 frames/second. This results in that a length of 1 hour as indicated by time code is longer than the actual clock time of 1 hour by 108 frames, or about 3.6 seconds. Drop frame mode adjusts the running of time code to eliminate this discrepancy, by dropping two frames from time code account at the beginning of each minute except every tenth minute. On the other hand, non-drop frame mode does not adjust the discrepancy between time code value and actual time.
drop frame time code – A type of time code designed to match a clock time exactly. Two frames of code are dropped every minute, on the minute, except every tenth minute, to correct for the fact that color frames occur at a rate of 29.97 per second, rather than 30 fps.
drop-in loading – camera system that automatically advances film to the first frame when the camera’s back is closed.
drop shadow – an effect in which an image appears to be slightly raised as if floating, caused by a shadow below it that is offset to one or two sides.
dry – 1. An actor forgetting the words of his script. 2. To record a sound without using any effect or other processing is to record it “dry”. Recording with an effect is recording “wet”.
dry mounting – a means of attaching a print to a backing using a thin paper stock coated on each side with a dry cement that melts under heat.
dual link – SDTV and HDTV in YUV 4:2:2 can be transmitted via a single BNC connector (single link). However, other video formats (e.g. RGB transmissions) exceed the data rate provided by a single BNC connector. For such a video signal two BNCs for a parallel (HD-)SDI connection are required, which is called a dual-link connection.
dub – To copy by playing back on one machine and recording on another.
dubbing – The process of copying the audiovisual signals from one magnetic tape onto another. Depending upon whether the medium is analog or digital, dubbed tapes can be duplicates or reproductions. Also: the process of adding sound to a silent video to complete a video production. See also migration.
duct tape – A shiny adhesive tape designed for holding metal heating and cooling ducts, but also commonly used as a substitute for gaffers tape, a general purpose tape used in television and film.
duophonic – (Two-sounds) A synthesizer that can play two notes or sounds at the same time is said to be duophonic.
duotone – a black and white (grayscale) image that has a single color added to it. “duo” refers to the two “colors” – black and the other color – that are combined in the image. in printing, two color plates (one black; one a color) are used to print a duotone image.
dupe, dupe negative, duplicate negative – 1. A duplicate negative made from a master positive. 2. A back-up or safety copy of a cut negative used for creating prints thus preserving the original negative. 3. A second generation internegative made from a master positive by printing and development or from an original negative by printing followed by reversal development.
duplicated – To say that a work can be duplicated implies that a copy could not be distinguished from the original by an independent observer. This behavior applies to artifacts that can be perfectly cloned, as in digital media, or to artifacts comprising ready-made, industrially fabricated, or mass-produced components. See also cloned; compare reproduced.
dust-busting – Removal of visible dust and scratches after film has been digitized.
dx – a coding system using a pattern of squares printed on a film cassette that can be read by a dx-enabled camera to automatically set film speed for the camera’s exposure meter, to set the number of frames and other data. also called “dx coding” or “dx encoding.”
dye – In photography, the result of color processing in which the silver grains or incorporated color couplers have been converted into the appropriate dye to form part of the color image.
dye sublimation printer – a printer that vaporizes ink onto the page, where it solidifies.
Dynamics – A branch of physics that describes how objects move using physical rules to simulate the natural forces that act upon them. Dynamic simulations are difficult to achieve with traditional key-frame animation techniques, but new technology lets you set up the conditions and constraints that you want to occur, and then automatically solves how to animate the objects in the scene.
dynamic microphone – 1. a pressure-sensitive microphone of moving coil design that transduces sound into electricity using electromagnetic principles. 2. a microphone which uses a magnet moving in a coil of wire to generate an electrical signal.
dynamic range – also known as tonal range. 1. The range of values between the darkest and brightest perceptible points in an image. An image containing very bright areas and very dark areas has a “wide” dynamic range. 2. In a black and white image, dynamic range refers to the various shades of gray between solid black and absolute white. 3. the measure of the range of brightness levels that can be recorded by a camera’s sensor. (see “clipping” for further info on overexposed areas of an image.) 4. The difference between the loudest and softest part in an audio recording, the maximum possible being determined by its sample format. For a device, the difference between its maximum possible undistorted signal and its Noise Floor.
dynamic simulation – 3D animation. Real world phenomena (such as friction) are imitated by using dynamic simulation. This is achieved by attaching physical properties (such as mass) to objects and manipulating forces that produce motion in objects over time. Forces include gravity and winds: local (fan) and global. Force intensity, direction, etc. may be animated. Collision detection: Normally, 3D objects pass through each other freely. With collision detection they don’t. This is achieved by defining obstacles for an object. For example, to bounce a ball down the stairs you first select the ball and then select the stairs as an obstacle. Then drop the ball: it detects the impacts and behaves accordingly.
dynamic voice allocation — permits voice channels to be automatically redirected to play other notes.