Business & Home Theater Projector Glossary: Everything You Need to Know
Published February 2016
From brightness and resolution to saturation and more, there’s a lot to think about when buying or using a projector. Whether it’s for home or business use, doing homework is key. Here’s your cheat sheet for the terms you’ll need to understand.
1080p 1080p is a high-definition 1920 x 1080 progressive scan video format where a complete frame of video is delivered at either 30 or 25 frames per second.
1:1 1:1 is one of the common aspect ratios used for projector screens. It is the most flexible as the projection area is square and can be adapted to whatever size is required.
3LCD Common 3 color system for projecting images via liquid crystal display (LCD). Uses dichroic mirrors to separate the RGB components of white light coming from a projection lamp. Each color is fed to separate LCD panels, which control the amount of colored light that passes through. The light from each LCD is recombined using a dichroic prism before going out the lens and onto a screen.
4:3 Aspect ratio of a standard TV signal, which is 4 units x 3 units, whatever size those units may be. In the film trade, aspect ratios are described in relation to one, which means this aspect ratio is described as 4/3 or 1.33:1.
16:09 The aspect ratio of an HDTV signal, which is 16 units x 9 units, whatever size those units may be. In the film trade, aspect ratios are described in relation to one, which means this aspect ratio is described as 16/9 or 1.78:1.
720p 720p is a high-definition 1280 x 720 progressive scan video format where a complete frame of video is delivered at either 60, 50, 30 or 25 frames per second.
Ambient Light Any light in the viewing room created by a source other than the projector or screen.
ANSI American National Standards Institute is a private organization that coordinates and administers various voluntary consensus standards, such as ANSI lumens. The first ANSI standard was for pipe threading in 1919 when it was called the American Engineering Standards Committee.
ANSI Lumens ANSI lumens is a measurement of the overall brightness of a projector. Because the center of a projected image is brighter than the corners, ANSI lumens are the most accurate representation of the image brightness. ANSI lumens are calculated by dividing a square meter image into nine equal rectangles, measuring the lux (or brightness) reading at the center of each rectangle, and averaging these nine points.
Aspect Ratio The ratio of image width to image height. Standard television is 4:3 or 1.33:1. Panavision or Cinemascope is 2.35:1, with 1.85:1 being quite common as well. Wide-screen displays are 1.78:1 or 16:9 times the height. For example, if you want an image 40” high, then you need a screen that is at least 40 * 1.78” wide or 71”. Other relatively common aspect ratios are 3:2, 4:3 and 5:4.
Brightness Overall light output from an image. While a brightness control can make an image brighter, it is best used to better define the black level of the image.
Color Saturation The measure of color purity; highly saturated colors emit a very narrow band of wavelengths of light instead of the broader spectrum of frequencies emitted from mixed colors. A display with good saturation capability will look vibrant.
Color Wheel A rotating wheel with three or more translucent color filters used to display sequential color on single imager light valve-based projection devices. The imager reflects or transmits the color component of a given image when the wheel’s corresponding color filter is affecting the light passing through to the lens. A 1X wheel cycles through all colors in 1/60th of a second.
Contrast Contrast increases as the white point increases. Increasing the white point creates a greater difference between white and black.
Contrast Ratio The ratio between white and black. The larger the contrast ratio, the greater the ability of a video device to show subtle color details and tolerate ambient room light. There are two industry methods used: 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 video devices, 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 video device.
Diagonal The diagonal of a screen or flat panel can be computed by using the Pythagorean theorem: squaring the width, squaring the height, adding them together and taking the square root. A 100" diagonal 16:9 screen measures 49" high by 87" wide; a 100" diagonal 4:3 screen measures 60" high by 80" wide.
DLP (Digital Light Processing) A commercial name for a display technology from Texas Instruments. The technology inside is often referred to as Digital Micro-Mirrors (DMD). It consists of an array of mirrors where each mirror represents a pixel element. For example, a high-definition DLP projector or rear projector with 1920 x 1080 pixel resolution would have over 2 million tiny mirrors. Each mirror is attached to an electronically driven hinge that controls the amount of colored light that is reflected from the mirror into the projection lens and onto a screen. Projection systems using DLP technology use 1 to 3 DMD devices.
DVI (Digital Visual Interface) DVI is a standard that defines the digital interface between digital devices, such as projectors, flat screens and personal computers. For devices that support DVI, a digital-to-digital connection can be made that eliminates the conversion to analog and delivers an unblemished image. It can also carry an analog signal and comes as DVI-I (integrated –– analog and digital), DVI-D (digital only) and DVI-A (analog only). Dual link DVI connections add additional resolution capabilities. Digital cable lengths should not exceed 5 m. Specifications on DVI are available at www.ddwg.org
HD (High-Definition Television) Generic term that indicates a higher resolution format than previous standards. At present, denotes anything higher than a 480p signal. Most common formats are 720p, 1080i and 1080p.
HDMI (High-Definition Multimedia Interface) is an uncompressed, all-digital audio/video interface that supports audio/video sources, including a set-top box, DVD player, A/V receiver, and video monitors such as a digital projector or digital television (DTV). HDMI is backward compatible with DVI 1.0 specification and supports HDCP. HDMI supports standard, enhanced or high-definition video, plus multichannel digital audio and interactive controls on a single cable. It transmits all ATSC (Advanced Television Systems Committee) HDTV standards and supports 8-channel digital audio.
Horizontal Resolution The amount of pixels across an image, from left to right. A 1920 x 1080 HDTV has a horizontal resolution of 1920 pixels.
Keystone Correction A method that makes a projected image rectangular. This can be accomplished by positioning the projector to be perpendicular to the screen. Since this is not always possible, most projectors are equipped with keystone correction that allows the image to be keystone corrected (made rectangular) by adjusting optics, making mechanical adjustments, or applying digital scaling to the image. Keystone correction can be one or two dimensional and manual or automatic, depending on the projector and the manufacturer. Be aware that digital scaling will introduce some artifacts that are more evident when viewing small text and less evident in presentation type material or video.
Lamp All projectors require a light source and most LCD and DLP projectors use a lamp (bulb); its power is measured in watts.
Lamp Life The average expected life of a lamp used in a particular projector.
LED (Light Emitting Diode) A light generating technology that uses a semiconductor diode that emits monochromatic (single color) light when charged. LEDs are used in remote controls that control electronic devices, such as large displays.
Lumen A measurement unit of total illumination. Typically a 100-watt lightbulb outputs 1700 lumens over a wide area. Projector light output is measured in ANSI lumens. A projector with a higher number will produce a brighter image for a given image size. (See ANSI Lumens.)
Mini Jack A 3.5 mm plug for connecting stereo audio in a smaller space than conventional two RCA jacks.
Native Aspect Ratio Nearly every projector or display today will support multiple aspect ratios; however, manufacturers must decide who their intended audience is and optimize the projector for that audience. This means each device has a native aspect ratio that is optimized for specific viewing material. Images shown in native aspect ratio will utilize the entire resolution of the display and achieve maximum brightness. Images shown in other than native aspect ratio will always have less resolution and less brightness than images shown in native aspect ratio.
Native Resolution 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.
Rainbow Effect An image anomaly that can be seen by a small percentage of people when viewing a single-chip DLPTM front or rear projection system. The anomaly appears as a color breakup at the edge of objects when the eye transitions rapidly between light and dark areas of the image. The problem is characteristic of sequential color systems with low refresh rates.
RGB (Red, Green and Blue) A component signal representing each color separately. Sync signals can be sent on green or sent separately as a composite signal or dual H/V signals (Horizontal sync/Vertical sync).
RJ45 A computer network connection allowing communication between units attached to the same network for control or information sharing.
Saturation Saturation is a measure of color intensity. In the absence of saturation, the color hue is a shade of gray. A highly saturated hue has a vivid, intense color, while a less saturated hue appears more muted and gray.
Short Throw Lens A lens designed to project the largest possible image from a short distance. Most front projection systems use a short throw lens and are required for rear projection where the depth behind the screen is limited.
SVGA A display resolution measuring 800 pixels horizontally by 600 pixels vertically, giving a total display resolution of 480,000 individual pixels. SVGA has a 4:3 aspect ratio.
Throw Ratio The ratio between the projection distance and image width. For example, a throw ratio of 2:1 means to achieve every unit of screen width requires two units of projection distance. Normally quoted as a range as most projectors have a zoom facility.
UXGA A display resolution measuring 1600 pixels horizontally and 1200 pixels vertically, giving a total display resolution of 1,920,000 individual pixels. UXGA has an aspect ratio of 4:3.
Viewing Angle The range of angle relative to a screen that an image can be fully viewed at a minimum of 50% of its original brightness. It is the midpoint of the angle being perpendicular to the screen.
Wi-Fi (Wireless Fidelity) A type of wireless network used to connect digital devices without the need for cables. It is mostly used for wireless broadband access, and inexpensive consumer wireless antennas are available at electronics stores. There are four specifications currently in the family: 802.11, 802.11a, 802.11b and 802.11g.
Wide Screen Any aspect ratio that is wider than 4:3. Wide-screen televisions are 16 units wide and 9 units tall. Common wide-screen film aspect ratios are 1.66:1, 1.85:1 and 2:35:1.
WXGA Display 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 pixels that a display uses to create an image. A WXGA display has 1366 to 1280 pixels horizontally and 768 to 720 pixels vertically.
XGA Display A display resolution measuring 1024 pixels horizontally and 768 pixels vertically giving a total display resolution of 786,432 individual pixels. XGA has a 4:3 aspect ratio.