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Graphics and Design Terms Glossary A — K
Knowing graphics and design terms are important because "speaking the same language" always helps things along. For both clients and novice designers it is important to be aware of graphics and design terms and expressions to ensure that projects are being both designed and quoted properly. For instance a grayscale image looks black and white ... yet in terms of creating an image, the differences between a black & white and gray scale image is considerable! For these reasons this glossary of terms will help ensure clear communication, accurate project quotes and expected results Fees may vary depending upon whether the agreement is a "one-off" or package / development project ...no different than a "volume discount." Terms Glossary A Achromatic : Light without color. The quantity of light is the only attribute associated with achromatic light. In physical terms this is the intensity or luminance or in the psychological sense it is the perceived intensity in which case the term brightness is used. Additive Color Model : In an additive color model, colors are defined as a sum of contributions from primary colors. The most commonly used additive color model is the Red-Green-Blue model and is used by computer monitors to produce their display. Additive Primaries : Red, green, and blue (RGB). Lights of these colors, when mixed together in varying intensities, produce any other color in the additive color model. Alpha Channel : The top byte of a 32-bit pixel that is used for data other than color. The channel may hold mask or transparency data. Ambient Light : A global (artificial) illumination level representing infinite diffuse reflections from all surfaces within a scene ensuring that all surfaces are visible (lit) particularly those without direct illumination. Animation : (1) A medium that provides the illusion of a moving scene using a sequence of still images. (2) Techniques used in the production of animated films. In computer graphics this primarily concerns controlling the motion of computer models and the camera. Anti-aliasing : Anti-aliasing is a method of reducing or preventing aliasing artifacts when rendering by using color information to simulate higher screen resolutions. In one technique, blurred pixels are introduced by filtering the image, or individual elements. The blending of pixel colors on the perimeter of hard-edged shapes, like type, to smooth out undesirable edges (jaggies). Artifacts / Artifact : A classifiable visual error. E.g., a loss of resolution when zooming into an image or incorrect depth sorting due to the painter's algorithm. ASCII : (American Standard Code for Information Interchange) A standard editable format for encoding data. Aspect Ratio : The ratio of the width of an image to its height (x:y). For example, the aspect ratio of an image 640 x 480 pixels is 4:3. Atmospheric Effects : Atmospheric conditions or phenomena that effect the clarity or mood of a scene. Fog and smoke are examples of atmospheric effects. Axis : The Hypothetical linear path. The X, Y, and Z axes (width, height, and depth, respectively) define directions of the 3D universe. The axis along which an object is rotated is the axis of rotation. B Backdrop : A picture that is automatically composited behind a 3D scene. The matte paintings used in traditional movie making are an example of backdrops. Bezier Curve : (1) A spline curve that (in the usual case of a cubic Bézier curve) is represented by four control points defining a cubic polynomial. (2) A curved line segment drawn using the Pen tool that can be reshaped by manipulating its anchor points or direction lines. Binary : In PhotoShop, it is a method for encoding data. Binary encoding is more compact than ASCII encoding. Binary Digit : A binary digit is the smallest unit of information on a computer. Eight bits equal one byte. Bit Depth : The number of bits used to define the shade or color of each pixel in an image. A 1- bit image is black and white. An 8-bit grayscale image provides 256 shades of gray. An 8-bit color image provides 256 colors. A 24-bit image provides over 16 million colors: 8 bits are used for red, 8 are for blue, and 8 for green. Bits per Pixel : The number of bits used to describe the color or intensity of a pixel. For example, using 8 bits for to store a value from the RGB color model would permit 3 bits to be used for both red and green values and 2 bits for the blue value. Blue gets a smaller range because the human eye contains less blue cones and is thus is less sensitive to blue variations. Bitmap : Strictly a one-bit-per-pixel representation for a defined area of a display. In PhotoShop, Bitmap is also a one-channel mode consisting of only black and white pixels. Blur : Reduces areas of high contrast to soften an image. Boolean : An object created by combining two objects using mathematical operators. The two object may be subtracted from each other, merged, or intersected to form the new object. Bounding Box : The smallest regular shaped box that encloses an object, usually rectangular in shape. Brightness : (1)The perceived intensity of a radiating object. (2) The amount of light reflected by a surface. (3) The intensity of a light source. (4) The luminance of a color. Brush : Traditionally in art, a brush is an implement that has hairs or bristles firmly set into a handle and used to paint with. In Photoshop, Painter and other computer graphics applications the brush is a virtual tool replicating the functions of its real world counterpart. Virtual brushes (depending on the program used) can emulate anything from a hard edge pencil, to soft edge airbrush effects, to crayons, oils, watercolor or even impasto style strokes. In most programs you usually have control over the characteristics of the brush stroke and you can also create custom brushes. When using pressure sensitive devices such as a graphics tablet, different characteristics of your brush stroke such as width and opacity can be controlled by factors such as pressure and pen tilt (depending on the device). Bump Mapping :  A technique used to increase the realism of a surface by changing how light reflects from that surface. Usually, the surface normal at a given point on a surface is used in the calculation of the brightness of the surface at that point. Part of what gives this techniques its appeal is that the original surface maintains its original (usually smooth) shape, and the bump-mapping distortion is specified by a compact function of shape. This is usually much simpler and more compact than specifying the surface texture by explicitly representing the textured surface. Burn : A PhotoShop tool that is used to darken an area of an image. C  [Top] CAD : Abbreviation of Computer Aided Design. In the context of graphics, CAD refers to the use of computer based models of objects for visualization or testing as an aid in the design process. Calibration : The process of setting a device to known color conditions. Calibration must be performed externally for devices whose color characteristics change frequently. For example, calibration must be performed on monitors because phosphors lose brightness over time, and on printers because proofers and other digital printing devices can change output when colorant or paper stock is changed. Calibration is not required for most input devices (e.g., scanners and cameras) since these devices are generally self-calibrating. Camera : A virtual viewpoint in world space with position and view direction to provide a view of a scene in the same way as a photographer would position a camera. Canvas : A two-dimensional region of graphics information. The canvas may be displayed on screen or be recorded in off-screen display memory. Canvas Size : The full editable area of an image. Caustics : The concentrated light reflections caused by refraction through a transparent surface. Channel : An image component that contains the pixel information for an individual color. A grayscale image has one color channel, an RGB image has three color channels, and a CMYK image has four color channels. Chroma : (1) A characterization of how much a color differs from both the pure color and the grey of the same intensity. Also called saturation. (2) The color component of a composite video signal. (3) The quality of a color that is the combination of hue and brightness. In the Munsell system of color notation, chroma indicates the purity of a color as measured along an axis; the farther from the axis, the purer the color. Clipboard : An area of memory used to temporarily store selection pixels. The Clipboard is accessed via the Cut, Copy, and Paste commands. Clipping : (1) The selective removal of an object disjoint with the display area or the non-visible parts of an object that does intersect the display area. Parts of an object intersecting the display area may lie outside of the display area or be partially or fully obscured by another intersecting object. (2) Color shift caused by the inability of one color space to reproduce all the colors of another color space. (3) In PhotoShop, the automatic adjustment of colors to bring them into printable gamut. CMYK : (Cyan, Magenta, Yellow, and Black) The four-ink colors used in process printing. Cyan, magenta, and yellow are the three subtractive primaries. CMYK colors are simulated on a computer monitor using additive red, green, and blue light. To color separate an image from PhotoShop, convert it to CMYK Color mode. CODEC : Algorithms used in multimedia. Stands for Compression/Decompression. Color Correction : The adjustment of color in an image to match original artwork or a photograph. Color correction is usually done in CMYK Color mode in preparation for process printing. Color Keying / Chroma Keying : Using the pixel color of one image to designate that pixel data from another image should replace the first pixel's color. The first image might be a binary image, which would select regions of interest from the second image. Another use is in blue- screening, where an actor works against a blue background. In the output image, the blue pixels get replaced by another image. For example, a weather map can be placed behind the weather presenter who is actually standing in front of a blue screen. Color Models : A color model is a method of specifying a color (position) in color space, often using a co-ordinate system. Examples include RGB and the Munsell Color System. Color Separation : The production of a separate printing plate for each ink color that will be used to print an image. Four plates are used in process color separation, one each for Cyan, Magenta, Yellow, and Black. An addition plate is used for each spot color. Color Space : A mathematical space defining a range and encoding of colors. E.g. see RGB, LUV, HSV, HSL, YIQ, YUV and XYZ. Color Table : The color palette of up to 256 colors of an image in Indexed Color mode. Composite Printer : The printer used to make a composite color image of a file. This printer can be used for proofing or for final output. Compositing : The process of combining multiple images into a single image. Usually this is performed in films to make a computer graphics generated character appear on a previously filmed background. The term is also used in traditional photographic manipulation to refer to the process by which cell animation is recorded onto film under a rostrum camera. In film the 'mechanical' process is usually called matte photography (see color keying), and the process, when used in film sequences is ambiguously called traveling matte. Compression : The process by which some of an image's data is either stored in patterns or eliminated in order to reduce the images file size. Continuous-Tone Image : An image, such as a photograph, in which there are gradual transitions between shades or colors. Contract Proof : The proof (e.g., Dupont WaterProof or Imation MatchPrint) of a color printing job that is the basis of a contract between a printer and a client. The appearance of the contract proof should represent the appearance of final printed piece. Contrast : The range of colors in an image. Increasing the contrast of a color palette makes different colors easier to distinguish, while reducing the contrast makes them appear washed out. Crop :  A tool used to trim away part of an image. Crop Marks : Short, fine lines that are placed around the edges of a page to designate where the paper is to be trimmed at a print shop. D  [Top] Data Rate : Transfer speed of a specific device. DCS 2.0 : (Desktop Color Separation) A file format for saving a CMYK image for color separation, with the option for saving spot color channels and alpha channels, and an optional low resolution file for previewing and laser printing. Depth of Field : The distance between the closest and farthest objects in focus within a scene as viewed by a lens at a particular focus. Diffuse : Light that is reflected from an object's surface, regardless of the angle from witch its viewed. Dissolve : An animation effect that is a transition between two sequences involving a fade from one directly to the other. Dither : The mixing of adjacent pixels to simulate additional colors when available colors are limited, such as on an 8-bit monitor or an 8-bit palette. Dithering : One of many processes for reducing the total number of colors present in an image while retaining visual fidelity. Dithering can be done by interleaving pixels of selected colors to locally approximate the desired color. Dithering can be applied to either a color or a grayscale color space and may be necessary due to a limited number of colors available on the display device. Dodge : To bleach (lighten) an area of an image. Dot Gain : Measured by the increase in size of a mid-tone dot, the spreading of dots during plate-making or on a printing press as wet ink is pushed into the paper and possibly absorbed by it, which causes colors or shades to look darker. DPI : (Dots per inch) A unit that is used to measure the resolution of a printer or image setter. Dpi is sometimes used to describe the input resolution of a scanner, but "ppi" is the more accurate term. Duotone : A grayscale image that is printed using two plates to enhance its tonal depth. DXF : A standard 3D file format that was originally developed by Autodesk to exchange CAD data between various software applications. This format only offers support for basic geometric information. Dye Sublimation : A continuous-tone printing process in which a solid printing medium is converted into a gas before it hits paper. E  [Top] EPS : Encapsulated PostScript, the file format based on Adobe PostScript. Primarily used to define vector graphics (i.e., geometrical shapes), it can also be used to contain and provide instructions for rendering image (i.e., pixel-based) data. In the case of PhotoShop, an optional PICT or TIFF image for screen display is included too. EPS is a commonly used format for moving files from one application to another and also for color separation. F  [Top] Feather : Fades an area over a specified number of pixels. Fill/Flood Fill : These are techniques for coloring areas bounded by line edges. The algorithms that fill interior-defined regions (the largest connected region of pixels whose values are the same as a given starting pixel) are called flood fill algorithms. Filter : 1) An optical device that selectively attenuates the intensity of light passing through it according to the light's properties. Common filters attenuate light according to either wavelength or polarization state. 2) An algorithm that selectively modifies the intensity or color of image data according to the image's properties. 3) An element (software or hardware) which takes in a stream of data and produces a stream of results, on average one output for each input. Foreground Color : The color that is applied when a painting tool is used, type is created, or the stroke command is applied. Four-color Process : The printing process that reproduces colors by combining, cyan (C), magenta (M), yellow (Y), and black (K) inks. This process is alternately called four-color printing, CMYK printing, or process printing. FPS : Frames Per Second. The rate at which animations are displayed. Frame : A still two-dimensional image. Often a frame is a raster image as used in the frame buffer of a graphics display system. In computer animation frames per second is a measurement of the number of still frames displayed in one second to give the impression of a moving image. Frame Rate : The frame rate of a video source is determined by the speed at which it completes the rendering of a new image. This is limited by both the speed at which image data can be created and the rate at which video images can be presented on a display. For example the NTSC system redraws at 30Hz, PAL is 25Hz and computer displays are now usually 72-75Hz. Frame Size : A term used to refer to the dimensions of the array of pixels forming a frame of an animation, or alternatively the memory requirement and hence indirectly the resolution and dimensions. G  [Top] Gamma : The values produced by a monitor from black to white are nonlinear. If you graph the values, they form a curve, not a straight line. Gamma defines the slope of that curve at halfway between black and white. Gamma adjustment compensates for the nonlinear tonal reproduction of output devices such as monitor tubes. Gamut : The total range of colors produced by a device. A color is said to be "out of gamut" when its position in one device's color space cannot be directly translated into another device's color space. GIF : Graphic Interchange Format. This file format is commonly used on the internet. Gradient Fill : In PhotoShop, a graduated blend between the Foreground and Background colors that is produced using the Gradient tool. Grayscale : A color space where colors are represented by their luminance values only, i.e. saturation and hue are zero. An image that contains black, white, and up to 256 shades of gray, but no color In PhotoShop, Grayscale is a one-channel image mode. H  [Top] Halftone Screen : A pattern of tiny dots that is used for printing an image to simulate continuous tones. Hard Proof : The printed proof of a document created to preview how colors will look when reproduced on a specific output device, usually a commercial printing press. A hard proof may be produced using a laminate contract proofing system (e.g., Imation MatchPrint) or a tightly calibrated digital printer designed for proof creation. Highlight : The area of a glossy object over which specular reflection can be viewed. It is normally the color of the light source, not of the object. Histogram : A graph showing the number of pixels at each level of brightness in an image. HSB : A three-coordinate, device-independent color model. The HSB coordinates define colors in terms of Hue, Saturation, and Brightness. HSL/Hue-Saturation-Lightness : HSL, also known as HSI (Hue-Saturation-Intensity) is a color space used to represent images. HSL is based on polar coordinates, while the RGB color space is based on a three-dimensional Cartesian coordinate system. Intensity is the vertical axis of the polar system, hue is the relative angle and saturation is the planar distance from the axis. HSL is thought to be more intuitive to manipulate than RGB space. For example, in the HSI space, to change red to pink requires only changing the saturation parameter. HSV/Hue-Saturation-Value : A color space that describes color using three basis components: hue, saturation and brightness. Hue : The wavelength of light of a pure color that gives a color its name--such as red or blue--independent of its saturation or brightness. I  [Top] Illuminance : The amount of light falling into a patch of unit surface area. It is measured in lux. Imagesetter : A high-resolution printer (usually between 1,270 and 4,000 dpi) that generates paper or film output from a computer file. Image File Format : A representation (usually binary) used by a computer system as an agreed format to store an image. Examples of image file formats include the Graphics Interchange Format (GIF) and Tagged Image File Format (TIFF). Inbetweening : Inbetweening is the generation of intermediate transition positions from a given start and end point or keyframes. This technique is often used in animation, where a lead artist generates the beginning and end keyframes of a sequence (typically 1 second apart), a breakdown artist does the breakdowns (typically 4 frames apart), and an ‘inbetweener’ completes the rest. Indexed Color : In PhotoShop, an image mode in which there is only one channel and a color table that can contain up to 256 colors. All the colors in an Indexed Color image are displayed on its table. Indexed 16 and 256 Color Images : An indexed color image consists of a set of references to values stored in a color table or palette. The palette, which is often contiguous in an image file, lists all the colors as sets of coordinates in color space. An indexed 16-color image contains a palette with 16 color entries (4 bits), whereas in an indexed 256 color image 256 colors are listed (8 bits). Interpolation : A process that occurs automatically when an image's dimensions or resolution are changed which results in re-coloring the pixels. Interpolation may cause an image to look blurry when it's printed. You can choose an interpolation method in PhotoShop from slower, but better, to faster but lower quality. Interlaced Display : A technique for displaying images at a higher resolution than the monitor. Two images consisting of every second row of pixels are alternately displayed during every screen refresh (e.g. every fiftieth of a second). There is hence a flickering artifact. International Color Consortium (ICC) : The group established by eight industry vendors (including Adobe Systems) for the purpose of creating, promoting, and encouraging the standardization and evolution of an open, vendor-neutral, cross-platform color management system architecture. Inverse Kinematics (IK) : The study of how movement of a body part affects other attached body parts. Invert : To reverse an image's light and dark values and/or colors. J  [Top] JPEG : Acronym for Joint Photographic Experts Group. Commonly used to indicate a pixel- based graphic file format, JPEG is actually a compression method used mostly for continuous tone images. JPG : An image format commonly used on the internet. It does not support layers, transparency or alpha channel data. K  [Top] Kern : To adjust the horizontal spacing between a pair of characters. Keyframe : An image that is stored in some way to be used as a reference point. Key frames are often used in animation — Related Pages —  Logos & Crests  Technical & Creative Writing  Web Site Design  Illustration  Renderings  Public Relations  Advertising  TGD Services  Fee Schedule & Conditions  Download Graphic Apps  Download Utility Apps   Clip Art  Site Map  Mission Statement Confidentiality Statement  Contact  Links  Tactical Equipment  Privacy Policy  About  Partner Sites  Paul Jacobsen Resume Brief  Contents of this web site are Copyright © 1993 - 2009 Paul Jacobsen©™ [TGD] unless otherwise noted. Graphics produced with Xara Xtreme Pro 4. Tactical Graphic Design - Visual Communication Specialties - Vancouver, British Columbia, Canada.
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