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  Glossary Of Product Photography Terminology


Abstract  In the photographic sense, an image that is conceived apart from concrete reality, generally emphasizing lines, colors and geometrical forms, and their relationship to one another.
AE  Automatic Exposure
AE LOCK  Auto Exposure Lock - permits you to take an exposure meter reading from part of a scene and to keep the reading to apply it to the entire composition. The photographer first aims the camera at a specific area, takes a meter reading, "locks" in that reading using the camera's AE Lock, then recomposes the image and takes the picture.
AF  Abbreviation for 'Autofocus'
Ambient light  Existing light surrounding a subject; the light that is illuminating a scene without any additional light supplied by the photographer.
Analog:  An analog video signal uses a variable voltage to equal the pixel value, as opposed to digital pulses.
Anamorphic:  Process that horizontally condenses (squeezes) a 16:9 image into a 4:3 space, preserving 25 percent more vertical resolution than letterboxing into the 4:3 space. For the signal to appear with correct geometry, the display must either horizontally expand or vertically squish the image.
APERTURE  A circle-shaped opening in a lens (a hole, really) through which light passes to strike the film. The aperture is usually created by an iris diaphragm that is adjustable, enabling the aperture to be made wider or narrower, thereby letting in more or less light. The size of the aperture is expressed as an '-number, like '/8 or '/11.
Aperture:  In television optics, it is the effective diameter of the lens that controls the amount of light reaching the photoconductive or photo emitting image pickup sensor.
ASA  The now defunct film speed rating system of the USA Standards Institute, which was formerly called the American Standards Association
ASPECT RATIO  The ratio of a picture's length to its width.
Aspect Ratio:  The ratio of image width to image height. Common motion-picture ratios are 1.85:1 and 2.35:1. Television screens are usually 1.33:1 (also known as 4:3), which is similar to the Academy standard for films in the '50s. HDTV is 1.78:1, or 16:9. When widescreen movies (films with aspect ratios wider than 1.33:1) are displayed on 1.33:1 televisions, the image must be letterboxed, anamorphically squeezed, or panned-and-scanned to fit the screen.
AV  The Aperture value

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Backlighting  Light coming from behind the subject, toward the camera lens, so that the subject stands out vividly against the background.
Backlit:  Refers to a remote control, or on projector control panel, that has buttons and controls that are illuminated. This is a major asset when using the projector in a darkened or semi-darkened room. Many projectors have backlit remote controls, while the number of projectors with backlit control panels is much smaller. As projectors have gotten brighter, room lights tend to stay on, so while nice, having backlit controls is no longer important to many users.
Bandwidth:  In audio, the range of frequencies a device operates within. In video, the range of frequencies passed from the input to the output.
Black Level:  Light level of the darker portions of a video image. A black level control sets the light level of the darkest portion of the video signal to match that of the display's black level capability. Black is, of course, the absence of light. Many displays, however, have as much difficulty shutting off the light in the black portions of an image as they do creating light in the brighter portions. CRT-based displays usually have better black levels than DLP, plasma, and LCD, which rank, generally, in that order.
Bracketing  Taking a series of photographs of the same subject at different exposures to insure the correct exposure.
BRI (Basic Rate Interface):  The most common kind of ISDN interface available in the US. BRI contains two B channels, each with 64 kbps capacity, and a single D channel (16 kbps) which is used for signaling and call progress messages.
Brightness:  For video, the overall light level of the entire image. A brightness control makes an image brighter; however, when it is combined with a contrast, or white level control, the brightness control is best used to define the black level of the image (see Black Level). For audio, something referred to as bright has too much treble or high-frequency sound.

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CCD  Electronic sensor used by all autofocus cameras, capable of detecting subject contrast; also an image-receiving device for video camera.
Chromaticity:  The colour quality of light that is defined by the wavelength (hue) and saturation. Chromaticity defines all the qualities of colour except its brightness.
Chrominance:  The chrominance of a picture refers to its color saturation and hue.
Codec:  Mathematical algorithms used to compress large data signals into small spaces with minimal perceived loss of information.
Color Temperature:  A method of measuring the "whiteness" of a light source. Metal halide lamps have very high temperatures compared to halogen or incandescent lights.
Composite Video Signal:  The combined picture signal, including vertical and horizontal blanking and synchronizing signals.
Composite Video:  A signal that contains both chrominance and luminance on the same 75-ohm cable. Used in nearly all consumer video devices. Chrominance is carried in a 3.58-mHz sideband and filtered out by the TV's notch or comb filter. Poor filtering can result in dot crawl, hanging dots, or other image artifacts.
Contrast Ratio:  The ratio between white and black. The larger the contrast ratio the greater the ability of a projector to show subtle color details and tolerate extraneous room light. There are two methods used by the projection industry: 1) Full On/Off contrast measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image. 2) ANSI contrast is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing the contrast ratio of projectors make sure you are comparing the same type of contrast. Full On/Off contrast will always be a larger number than ANSI contrast for the same projector.
Contrast:  Relative difference between the brightest and darkest parts of an image. A contrast control adjusts the peak white level of a display device.

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decibel  dB or decibel is a measure of the power ratio of two signals, provided they are measured across a common impedance.

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Dolby Digital:  An encoding system that digitally compresses up to 5.1 discrete channels of audio (left front, centre, right front, left surround, right surround, and LFE) into a single bitstream, which can be recorded onto a DVD, HDTV broadcast, or other form of digital media. When RF-modulated, it was included on some laser discs, which requires an RF-demodulator before the signal can be decoded. Five channels are full-range; the .1 channel is a band-limited LFE track. A Dolby Digital processor (found in most new receivers, preamps, and some DVD players) can decode this signal back into the 5.1 separate channels. Most films since 1992's Batman Returns have been recorded in a 5.1 digital format, though a number of films before that had 6-channel analogue tracks that have been remastered into 5.1.
DVI:  Digital Visual Interface. Connection standard developed by Intel for connecting computers to digital monitors such as flat panels and DLP projectors. A consumer electronics version, not necessarily compatible with the PC version, is used as a connection standard for HDTV tuners and displays. Transmits an uncompressed digital signal to the display. The latter version uses HDCP copy protection to prevent unauthorized copying. See also HDMI.

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EXIF  Besides information about the pixels of the image, most cameras store additional information such as the date and time the image was taken, aperture, shutterspeed, ISO, and most other camera settings.
Exposure  The exposure is the amount of light received by the film or sensor and is determined by how wide you open the lens diaphragm (aperture) and by how long you keep the film or sensor exposed (shutterspeed).

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Fader:  The control on a projector that allows you to control the balance of sound between the projectors internal speakers and the external speakers (PA, powered speakers). Only a couple of projectors offer this convenient feature.
Focal Length:  The distance from the surface of a lens to its focal point.
Focus:  The focus on a projector defines the minimum and maximum projection distances.
Frame Rate:  Number of images per second displayed in a video stream. Approximately 24 frames per second (fps) is considered full-motion video.
FXL:  The most popular halogen lamp in use in lower cost projectors and overhead projectors. The lamps typically last about 40 hours, however for convenience, most projectors using halogen lamps carry a spare, and a quick method of going to the backup lamp. Metal halide lamps and UHP lamps are used in most of the medium and higher priced, more powerful portables.

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HDTV:  High-Definition Television. There is no official definition, but usually refers to a 16:9 image with twice the horizontal and vertical resolution of existing system, accompanied by 5.1 channels of Dolby Digital audio. Other definitions include an image with 720 progressive or 1080 interlaced active (top to bottom) scan lines. 1280:720p and 1920:1080i are typically accepted as high-definition scan rates.
High-Definition television (HDTV) :  High-Definition television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. Except for early analog formats in Europe and Japan, HDTV is broadcasted digitally, and therefore its introduction sometimes coincides with the introduction of digital television (DTV).
HDTV is defined as 1080 active lines, 16 x 9 aspect ratio in ITU-R BT.709. However, in the ATSC broadcast standard used in the United States and other countries, any ATSC resolution with 720 or more active lines is considered HDTV.
Hz:  Hertz or cycles per second. Something that repeats a cycle once each second moves at a rate of 1 Hz.

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Infrared Remote:  The traditional remote control, it transmits infrared like a television remote. Typical range is limited to 30-35-ft. Infrared requires line of site or a bounce off of a hard surface. The presenter must pay attention to where the remote is pointed. Some projectors have an IR sensor in both the front and rear of the projector, which can help a bit. When working at or near the maximum distance pointing right at the receiver is necessary. Remember 'line of sight'. A person's head directly between your remote and the projector may be enough to render it unusable.
ISDN (Integrated Services Digital Network):  Completely digital telephone/telecommunications network which carries voice, data, and video over existing telephone network infrastructure. It is designed to provide a single interface for hooking up a phone, fax machine, PC, etc. See Also: How to Order ISDN
ISDN (Integrated Services Digital Network):  Completely digital telephone/telecommunications network which carries voice, data, and video over existing telephone network infrastructure. It is designed to provide a single interface for hooking up a phone, fax machine, PC, etc. See Also: How to Order ISDN

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Keystone:  A form of video image distortion in which the top of the picture is wider than the bottom, or the left is taller than the right, or vice versa. The image is shaped like a trapezoid rather than a rectangle.

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Lag Time  Lag time is the time between you pressing the shutter release button and the camera actually taking the shot.
LCD:  An LCD projector is a device utilized for displaying video images or data. They are the modern equivalent to the slide projector and overhead projector used in the past.
LCD (liquid crystal display) projectors usually contain three separate LCD glass panels, one each for the red, green, and blue components of the video signal. Light from a halogen lamp, which outputs an ideal color temperature and a broad spectrum of color is split by a prism into the three component colors. As light passes through the LCD panels, individual pixels can be opened to allow light to pass, or closed to block the light, as if each little pixel were fitted with a Venetian blind. This activity modulates the light and produces the image that is projected onto the screen. With a lens that \"projects\" the image on any flat surface and does not require large \"furniture\" (like a big TV would), LCD projectors tend to be smaller and much more portable than older systems. The best image quality can be accomplished with a blank white or grey surface to project on, and for this reason dedicated projection screens are often used.
LCD projection technology is the current leader of the pack, having captured the majority of the market share of all projectors sold. Most LCD projectors have three panels.
Long Throw Lens:  A lens designed for projection from the back of a room, or rather the back of a long room. Long throw lenses would be used a projection booth in the back of a theater, etc. A typical long throw lens might have to be 50 to 100 FT back to project a 10FT diagonal image.

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Maximum Resolution:  Maximum Resolution refers to the highest resolution that a given display device can support. If the Maximum Resolution exceeds the Native Resolution, , the image is usually scaled to match or approximate the Native Resolution of the projector. Some display devices allow pan and scan where rather than scaling the image, the display devices allows you to use the native resolution of the display to view portions of the higher resolution image. Scaling reduces the image resolution and produces some artifacts in the image that are more apparent when viewing text than graphics or video.
Metal halide:  Metal halide light bulbs give off a much brighter image and last longer than halogen. High-end, and some medium projectors now use metal halide bulbs.
Multiplex:  Multiplex allows you to split an image into several panels on a single screen.
Multiplexing:  The condensing of many signals into a few or one signal that still represents all of them. An LCD panel performs the de-multiplex function. It takes video signals that contain whole frames of video data and displays them as individual signals on each pixel.

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Native Resolution:  Native Resolution is the number of physical pixels in a display device. For example, an XGA display has a native resolution of 1024 physical pixels of resolution horizontally and 768 pixels vertically or 786,432 total pixels.
NTSC:  National Television Standards Committee. Government-directed committee that established the U.S. color TV standard in 1953. Also known, sarcastically, as Never Twice the Same Color or Never The Same Color due to the inherent difficulty in achieving proper color calibration.

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OEM:  Original Equipment Manufacturer. A company that gathers components from other manufacturers and sells under their own name. An OEM version of a product is supported by the seller, not the actual manufacturer.
OHP:  The common abbreviation for overhead projector.
Overhead Projector:  A device consisting of a light source, a transmissive or reflective platform, and a focusable lens assembly. An OHP is designed to project images from tranparencies or LCD projection panels onto a screen.

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PAL:  A European and international broadcast standard for video and broadcasting; higher resolution than NTSC.
Panorama  A broad view, usually scenic.
Passive Matrix LCD:  The original LCDs, these are controlled by a single processing system, for the whole screen, unlike active and poly-si, which have discrete circuits for each "pixel." This results in a panel with terrible color dynamics and contrast (typically 15:1). They are also incredibly slow: On passive laptop computers, the cursor (or anything else) moving on the screen, goes invisible until you stop moving it (submarining) Only one or two projectors use any type of passive matrix display.
PBX (Private Branch Exchange):  Small version of the phone company's larger central switching office. A PBX is a private telephone switch. It is connected to groups of lines from one or more central offices and to all of the telephones at the location served by the PBX.
Pixel:  A pixel is a small dot that represents a single element of a display.
Plasma:  Flat-panel display technology that ignites small pockets of gas to light phosphors.
Polarized light  Light waves vibrating in one plane only as opposed to the multi-directional vibrations of normal rays. Natural effect produced by some reflecting surfaces, such as glass, water, polished wood, etc., but can also be simulated by placing a special screen in front of the light source. The transmission of polarized light is restrained by using a screen at an angle to the plane of polarization.
Pulse Code Modulation: (PCM)  Pulse Code Modulation: (PCM) a way to convert sound or analog information to binary information (0s and 1s) by taking samples of the sound and record the resulting number as binary information. Used on all CDs, DVD-Audio, and just about every other digital audio format. It can sometimes be found on DVD-Video.

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QXGA:  QXGA is the resolution of 2048 x 1536 pixels.

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Rainbow Effect  The DLP "Rainbow Effect"
This visual artifact is best described as brief flashes of perceived red, blue, and green "shadows" observed most often when the projected content features bright/white objects on a mostly dark/black background (the scrolling end credits of many movies being a common example). Some people perceive these rainbow artifacts all of the time, while others say they only see them when they let their eyes pan across the image. Yet others do not notice the artifact at all.
RAW  A digital image format that contains the most information possible from a camera's sensor.
RCA Jacks:  Receptacles for coaxial cables carrying line-level audio signals. Also called phono-type connectors.
Rear Screen Projector:  Using an opaque screen, the projector is placed behind the screen, invisible to the audience. It projects onto the screen and the audience sees it on the other side. Good rear projection screens actually produce brighter images than some standard screens. So as not to waste space behind the screen, ideally a projector with a short throw lens is used. Since the projector can be placed even with the middle of the screen, without blocking anyone's view, keystoning is not a problem. Some mid-room projectors have available third-party short throw lenses. Since the image is projected through the screen, the image must be reversed.
Red eye  An image in which a subject’s irises are red instead of real color.
Reflex Camera  A camera that has a mirror directly in the path of light traveling through the lens that reflects the scene to a viewing screen.
Refresh Rate:  The speed at which a display updates its picture given in Hz.
RGB:  Red, Green, Blue. Can refer to an unprocessed video signal or the colour points of a display device. Together these three colours make up every colour seen on a display device.
Ring Flash  A circular-shaped electronic flash unit that fits around a lens and provides shadowless, uniform frontal lighting, especially useful in macro photography.
RJ11, RJ45, or RJ48  Different types of jacks,can be used for an ISDN line. The RJ11 is the most common in the world and is most often used for analog phones, modems, and fax machines. RJ48 and RJ45 are essentially the same, as they both have the same 8-pin configuration. An RJ11 jack can fit into an RJ45/RJ48 connector, however, an RJ45/RJ48 jack cannot fit into an RJ11 connector.

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S-VHS:  Super VHS. Enhancement to regular VHS that offers improved luminance resolution. (400 lines or so.)
S-Video:  A video transmission standard that uses a 4-pin mini-DIN connector to send video information on two signal wires called luminance (brightness, Y) and chrominance (color, C). S-Video is also referred to as Y/C. A composite signal, typically found coming out of an RCA jack on the back of most VCRs has the Y and C information combined into one signal. The advantage of having luminance and chrominance separated is that a comb filter is not needed inside the video projector to separate the composite signal into the luminance and chrominance signals. A comb filter can reduce the sharpness of your video image.
Screen Door Effect :  The Screen Door Effect or FPN (Fixed Pattern Noise) is a visual artifact of the projection technology use in digital projectors, where the fine lines separating the projector's pixels become visible in the projected image. This results in an image that appears as if viewed through a screen door. It can appear as a grid like structure or as a hexagonal structure.
SECAM:  A French and international broadcast standard for video and broadcasting; higher resolution than NTSC.
Short throw lens:  A short throw lens is designed to project the largest possible image from a short distance.
Skew:  A signal distortion where one part of a signal arrives at a different time than another and causes color fringes to the sides of an object.

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sRGB:  Standard Red, Green, and Blue, and is a standard for rendering color evenly across a variety of platforms.

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Subwoofer:  A speaker designed to reproduce very low bass frequencies, usually those below about 80 Hz.
SVGA:  SVGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. An SVGA display has 800 horizontal pixels and 600 vertical pixels giving a total display resolution of 480,000 individual pixels that are used to compose the image delivered by a projector.
SXGA:  SXGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. An SXGA display has 1,280 horizontal pixels and 1,024 vertical pixels giving a total display resolution of 1,310,720 individual pixels that are used to compose the image delivered by a projector.

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Tabletop  Any item which easily fits on a 6' square table.
TFT:  Thin Film Transistor
TFT:  Thin Film Transistor. A type of LCD display where each pixel is controlled by one to four transistors. TFT screens are sometimes called active matrix LCDs.

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UV  The ultra violet ray. This is beyond the visible spectrum.
UXGA:  UXGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. A UXGA display has 1,600 horizontal pixels and 1,200 vertical pixels giving a total display resolution of 1,920,000 individual pixels that are used to compose the image delivered by a projector.

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VCR:  Video Cassette Recorder.
VGA:  VGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. A VGA display has 640 horizontal pixels and 480 vertical pixels giving a total display resolution of 307,200 individual pixels that are used to compose the image delivered by a projector.
VHS:  Vertical Helical Scan (or as JCV calls it, "Video Home System"). Widely used method of recording audio and video electrical signals onto magnetic tape.
Video Capture:  Process of converting analog video to digital video.
Video projector:  A video projector takes a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. Video projectors are widely used for conference room presentations, classroom training, and home theatre applications.
Video projectors may also be built into cabinets which use a rear projection screen to form a single unified display device, now popular for "home theater" applications.
Vignetting  Underexposure of image corners produced deliberately by shading or unintentionally by inappropriate equipment, such as unsuitable lens hood or badly designed lens. A common fault of wide-angle lenses, owing to reflection cut-off, etc. of some of the very oblique rays. May be caused in some long-focus lenses by the length of the lens barrel.

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Wi-Fi:  Wi-Fi is Wireless Fidelity and is based on the IEEE 802.11 specifications for wireless local area networks (WLAN) developed by a working group of the Institute of Electrical and Electronics Engineers (IEEE). There are four specifications in the family: 802.11, 802.11a, 802.11b, and 802.11g. All four uses the Ethernet protocol and CSMA/CA (carrier sense multiple access with collision avoidance) for path sharing.
WMA:  Windows Media Audio. Similar to MP3 but considered a more efficient compressor allowing for smaller file sizes for a given quality.
WXGA:  WXGA defines a class of XGA displays with a width resolution sufficient to create an aspect ratio of 16:9. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. A WXGA display has 1,280 to 1,366 horizontal pixels and 720 to 768 vertical pixels, respectively, that are used to compose the image delivered by the projector.

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XGA:  XGA is used to define a specific display resolution. Resolution is defined by the number of individual dots that a display uses to create an image. These dots are called pixels. An XGA display has 1,020 horizontal pixels and 768 vertical pixels giving a total display resolution of 783,360 individual pixels that are used to compose the image delivered by a projector.

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Zoom Lens Ratio:  The ratio between the smallest and largest image a lens can project from a fixed distance. For example, a 1.4:1 zoom lens ratio means that a 10-ft image without zoom would be a 14-ft image with full zoom. Conversely, a 10-ft diagonal image at 15 foot with no zoom would still be a 10-ft image at 21 foot at maximum zoom (15 x 1.4 = 21-ft). A zoom lens is not as bright as a fixed lens, and the higher the ratio, the less light output.
Zoom Lens:  A lens with a variable focal length providing the ability to adjust the size of the image on a screen by adjusting the zoom lens, instead of having to move the projector closer or further.
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