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Corel PostScript® Printing Glossary

This is a listing of some common and not so common terms that are used when dealing with printing in general. (This page is very long so please use the • top link at the bottom of each section to return to this section) Note: that some of the glossary terms have specific reference to or from the source and may not be industry standard; however, in some situations we have added a line or two in corection. We trust you will find the general information useful.

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Achromatic
Having no color; i.e., black, white or gray.
Additive Color
In additive color reproduction, three primary colors (red, green and blue) are combined in various intensities to produce all other colors. When the three primaries are added together, the result is white. Television and computer monitors use the additive color model. The opposite of additive colors is subtractive color.
Anti-alias
The procedure of filtering an image to remove jagged edges from shapes. Anti-aliasing fills in the jagged pixels with intermediate colors which produces smooth transitions between colors.
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Banding
A noticeable stair stepping effect seen on gradient or fountain fills.
Bitmap Graphic
An image composed of a series of pixels or dots. Scanners and paint programs, such as Corel PHOTO-PAINT®, generate this type of image. By contrast, CorelDRAW® creates images using vector objects which are shapes stored internally as mathematical equations.
Black Point
A color printing term specifying the blackness level relative to a four-color and a three-color black. A four-color black is produced by printing 100% cyan (C), 100% magenta (M), 100% yellow (Y), and 100% black. A three-color black is produced by using full amounts of the CMY inks only, and is, therefore, not as dark.
   A black produced by a full 400% TAC is darker than a CMY 300% TAC. The black point specifies the blackness level relative to these two references in a range from 0 to 1.0. A black point of 0.0 yields a black as dark as a three color black (CMY) while a black point of 1.0 yields a black as dark as black as a full four color black.
Bleed
The part of a printed drawing that extends beyond the edge of the page.
BMP
The filename extension for files in Windows® or OS/2® bitmap format.
Brightness
In the HSB color model, brightness is the component that determines the amount of black in a color.
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CDR
The filename extension for the CorelDRAW vector-based file format.
CGM
This filename extension stands for Computer Graphics Metafile, a vector-based graphic file format.
Calibration
The process of adjusting a monitor, printer or scanner to display, print, and capture colors more accurately.
Channel
A channel is similar to a plate used in the printing process. Each channel represents a color. For example, if you have an RGB image, the channels are red, green, and blue. When all the channels combine, they mix to create the entire range of colors in the image.
Choke
One method of trapping, the other being a spread. In a choke, the knockout from the background is slightly shrunk, so that when the object that causes the knockout is printed, it slightly overprints the background.
Chromatic
Relating to color.
Chromaticity
Defines hue and saturation or chroma levels for your monitor.
Chromalin™
A high quality color proofing method.
CIE
A color model that is published by the Commission Internationale de l'Eclairage.
CMY
A color model made up of cyan, magenta and yellow. Use this color model if the drawing or image will be produced on a CMY device such as a three-ink printer.
CMYK
A color model made up of cyan, magenta, yellow and black. Cyan, magenta and yellow are the subtractive color primaries while black is used because equal proportions of CMY produce a muddy brown rather than a true black. K stands for black because it's sometimes referred to as the key, or registration, color.
Color Manager
A tool that learns about your monitor, scanner and printer to create a System Color Profile. This profile helps CorelDRAW capture, display and print color more accurately across different devices.
Color Model
A method by which a color can be described.
Color Proof
Sometimes called a prepress proof, this preliminary step in the color printing process shows how an image will look when it is printed. Proofing provides an opportunity to make corrections and adjustments before final printing.
Color Separation
The process of separating the colors in an image into the primary cyan, magenta, yellow and black.
Composite
Also referred as a "comprehensive" or "comp". This is a preliminary version of a design that combines all image, line art and text elements. Color composites are often printed on color PostScript® printers before they are color separated for four-color process printing.
Continuous tone
An image represented by smooth graduated tones from black to white as in a photograph.
Crop Marks
Alignment marks at the corners of a printed page. They are used as aids for press registration of colors and also for trimming the paper to its proper size.

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DCS
Desktop Color Separation. This image file format creates a PostScript file for each CMYK layer and a PICT or EPS preview file, resulting in five files for each color image.
Densitometer Scale
Scales that are printed on each page of a color-separated image to gauge the accuracy, quality and consistency of the output. These scales are available in the Print Options dialog box.
Dots Per Inch (dpi)
A measure of a printer or scanner's resolution. Typical desktop laser printers print at 300 dpi, while imagesetters are capable of printing at resolutions of 1270 or 2540 dpi.
Dot Gain
Occurs when the halftone dots in a screen reproduce larger on paper than specified in the program in which they were generated. A dot gain typically occurs when the plate is made and especially when the ink is laid down on the paper while printing. This can cause over saturated colors and inaccurate reproduction. Dot gain is expressed as the percentage increase in density from the time the screen density is specified to the time it is output on paper. A 50% screen that prints at 60% is said to have a dot gain of 10%.
Dropout
Another term for knockout.
Duotone
A grayscale image that has been converted into a two-color image (usually black + one PMS color). Using two colors of ink instead of four, significantly reduces the costs of printing while still providing a wide range of colors to choose from. The duotone feature is ideal for adding an accent color to a photograph or for extending the tonal ranges of inks.
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Emulsion
The light sensitive coating material of a piece of film.
EPS
The filename extension for Encapsulated PostScript files, a format created by Adobe®.
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Film Recorder
A device that reproduces images from a computer screen on photographic film, for either slides or prints using conventional photographic processes.
FOCOLTONE
A color system that provides a range of spot color built with the process CMYK colors. The FOCOLTONE colors are organized so that you can choose FOCOLTONE colors with at least 10% of one process color in common with another FOCOLTONE color. This minimizes the need for trapping, and makes it an ideal color palette to use for color separating.
Fountain Fill
A fill that fades gradually from one color to another. A Fountain fill may also be referred to as a Gradient or Graduated fill.
Four-Color Process
The four-color printing process, or process color, reproduces all color artwork with just four colors-cyan, magenta, yellow and black, often referred to as CMYK.
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Gamma
The degree of contrast seen on a computer monitor.
Gamut
A range of colors that a device can reproduce. Printers and output devices have limited gamuts.
Gamut Mapping
The reassigning of colors outside of the range of colors a device is capable of reproducing. The range of colors you specify from a palette or capture with a scanner can be larger that a printer can reproduce.
Gray Component Replacement (GCR)
The substitution on black ink for the cyan, magenta and yellow mixture that makes up the graying (achromatic) component of any color. Because it takes less black to darken a color than it would take cyan, magenta or yellow or some combination of these colors, the overall ink coverage is reduced. The increased black ink content is used to create the image shape and detail while the color serves more to color the image than to darken it.
   Another advantage of GCR is that it tends to make neutral tones more stable. It also allows the printer to decrease the ink coverage of cyan, magenta or yellow on the press to correct the way a particular part of an image is printing, without introducing a color cast to neutral areas elsewhere in the image.
Grayscale Image
An image in which tones are represented as shades of gray.
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Imagesetter
A generic term for printers capable of printing text and graphics at resolutions of 1200 dpi or higher on film or photographic paper.
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JPEG (Joint Photographic Experts Group)
An international standard for image compression that offers compressions with almost no losses at ratios up to 20:1.

Knockout
Occurs when the image area on one separation is left open on another separation. For example, to display yellow type on a black background, the type must be knocked out of the black or the yellow type will be obscured by the black background.
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Limitcheck Error
A PostScript printing error that occurs when a drawing contains too many line segments or too large a bitmap for the printer to reproduce.
   Corel applications provides a Flatness control in the Print Options dialog box that helps to overcome this problem.
Lines Per Inch (lpi)
The screen frequency used for photos and tints is described in lpi.
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Matchprint (3M)
A high-quality color proofing method.
Moiré Pattern
An undesirable wave pattern generated in an image printed from color separations with incorrect halftone screen angles.
Monochrome
An image containing one single color, usually black.
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Negative
An image in which the values in the original are reversed so that black areas appear white, white appears black and colors are represented by their complements.
Nested PowerClips
When you use a PowerClip object as a Contents object and place it inside a container, you create a nested PowerClip, or a PowerClip within a PowerClip. You can place a nested PowerClip inside another container, creating 2 levels of nesting, and so on. The maximum number of nested levels allowed is five.
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Offset Printing
The most traditional method of printing. This process involves the transfer of ink onto a reverse-reading plate to a positive-reading blanket and then onto the paper.
Open Prepress Interface (OPI)
A method for placing a high-resolution bitmap on the printed page, while using low-resolution bitmap for placement. Service bureau scans images on a high-end scanner, they keep the high-resolution version of the scans and give you low resolution equivalents. You import the low resolution images into your documents, using them for position only. Working with low resolution images keeps your document size smaller and speeds up screen redrawing time. When you send your artwork back to the service bureau for final imaging to film, our high resolution files are automatically substituted. The service bureau needs to have an OPI server in order to render these images.
Out-of-Gamut Color
A color that is available in the color space of the source device (e.g., your monitor) but is not available in the color gamut of the destination device (e.g., your printer).
Overprint
Occurs when one color is printed directly on top of another and their inks overlay one another. Overprints are often used with black or opaque colors, or when a mixture of two overlaid process colors is desired.
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PANTONE® Process Colors
Based on the CMYK color model. Therefore no additional plates are generated when creating color separations.
PANTONE® Spot Colors
Known also as the PANTONE Matching System (PMS). Since spot colors correspond to solid inks, each unique color applied to an object results in an additional color separation plate.
PICT
An image file format used frequently on the Macintosh® platform which may use up to four channels-red, green, blue and Alpha.
Pixel
Short form for picture element. Pixels are dots on a computer or television screen that combine to form an image. Computer images are created as an array of such dots, each having a specific color.
PostScript®
A page description language or protocol by which programs describe text and graphics to their output device (specification written by Adobe Systems).
PowerClip
The PowerClip command in CorelDRAW™ 5 and subsequent versions lets you paste an object inside another object. A PowerClip object can be a closed path, a group of objects or Artistic text. A bitmap can act as a contents object, but not as a Container object.
Press Gain
Another phrase for Dot Gain
Process Color
A color printing method in which all the printed colors are made by various combinations of cyan, magenta, yellow and optionally, black. Process color inks are highly transparent so that when they overlay each other on the paper, other colors are produced as clearly as possible.
Proof
A printed trial version of a graphic to see how it will look when output in its final form. Laser printers are commonly used to proof monochrome artwork while color artwork is often proofed on thermal color printers. High-quality proofing systems such as Chromalin™ (DuPont) or Matchprint (3M) can be used to proof color separations.
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Raster Image Processor (RIP)
An interpreter between a vector graphics workstation and a raster output device (printer, imagesetter, etc.). A RIP converts vector objects and bitmaps from graphics programs into machine pixels (bitmaps) at a given output resolution.
Registration Marks
Marks on paper or film used for aligning color separations. CorelDRAW automatically adds registration marks when printing color separations to a PostScript printer.
Resolution
A term referring to the number of dots per inch (dpi) the printer is capable of printing. The more dpi, the smoother the output and the greater the number of grayscales the device can describe.
RGB
An acronym for red, green and blue. These are the additive color primaries.
RIP
An acronym for raster image processor.
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Saturation
The purity of a color. The HSB color model uses saturation as a component that determines the purity or integrity of a color. The more hues used to mix a color, the duller the color looks.
Scanner
A device that converts images on a page or transparency into digital form.
SCT
A format that saves drawings in a 32-bit color format which can be processed or modified for output by high-end film houses and film recorders. SCT is ideal for color-separated images as it is a native 32-bit CMYK format.
SCODL (Scan Conversion Object Description Language)
A file format used by film recorders for making slides
Screen Angle
When printing color separations, the angles at which each of the four process colors are printed to avoid undesirable Moiré Patterns.
Screen Frequency
Measured in lines per inch (lpi). Screen frequency affects images such as photographs and tints of color. Your screen frequency will be of a higher quality when outputting to a higher resolution device.
Spot Color
A color printing method in which the colors are produced by mixing inks before applying them to the page. This allows very accurate color specification. Spot color inks are opaque so overprinting spot colors only serve to hide the inks being covered and increase the TAC. One of the most widely used spot color systems is the PANTONE® Matching System.
Spread
One method of trapping, the other being choke. In a spread, the foreground object is made slightly larger so that it overprints the background. This is done in CorelDRAW by adding an outline with the same color as the fill and having the outline overprint. In CorelDRAW (and some other graphics packages), only half the thickness of this outline will overprint.
Stripping
The traditional method of positioning film onto a flat for eventual platemaking.
Subtractive Color
In subtractive color reproduction, color is produced when white light falls on a colored surface and is only partially reflected back to the observer. A perfectly white surface reflects all wavelengths while black reflects none.
SWOP
The abbreviation for Specifications for Web Offset Publications. This standard was developed to ensure consistency in color printing.
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QuickDraw
The display language interface for Apple Macintosh systems. QuickDraw printers are compatible only with Macintosh systems and do not offer the performance and features available with Adobe PrintGear printers.
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TAC
An acronym for Total Area Coverage
TGA (Targa)
A bitmap format commonly used to store digitized color photographs.
TIFF (Tagged Image File Format)
A bitmap format commonly used to store digitized color photographs. This format can be rendered in color or grayscale.
Tile
To use multiple pages to print a drawing that is larger than the printer's paper size. This option may be selected in the Print Options dialog box when your drawing is larger that the printer's paper size. The results will give you multiple printed pages.
Total Area Coverage
A measure expressed as a percentage of the total amount of ink applied to a given area of a printout. If 100% of each of the CMYK inks are applied to the same area, the TAC is 400%. Similarly, if 50% of each of the CMYK colors were applied to the same area, the TAC would be 200%.
   In the perfect world, a press would be able to lay down 400% coverage with no problem, but we don't live in a perfect world. Inks may not be 'sticky' enough for 400% TAC to adhere to the paper properly especially considering that very little drying time is provided between the application of individual colors. The maximum acceptable TAC is 300% with more frequent recommendations in the 240% to 280% range.
TOYO Color Model
The range of colors offered here includes those that are reproduced using TOYO standard inks. These colors are defined using the L*a*b* color space and are converted to RGB for display and CMYK for printing.
Trapping
The process of adding a slight overlap between adjacent areas of color to avoid gaps caused by registration errors. Traps are also referred to as chokes or spreads.
TRUMATCH®
This system is based on the CMYK color model and, therefore, colors do not add additional color separation plates. Colors are organized by hue (red to violet), saturation (deep to pastel) and brightness (adding or removing black).
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UA
An acronym for Undercolor Addition
UCR
An acronym for Undercolor Removal
Undercolor Addition
Black printed with black ink alone can look too 'thin'. UA is a way some image-editing programs compensate for taking out too much color from dark or neutral areas when GCR or UCR is carried out. Small but equal proportions of cyan, magenta and yellow are added to the black to increase its richness and coverage.
Undercolor Removal
The replacement of equal proportions of cyan, magenta and yellow with black inks in the shadow tones of an image. This is done primarily to reduce the total ink coverage on the press and to give blacker blacks.
   UCR is used in dark or black areas. CMY values aren't usually totally replaced by black because pure black looks 'thinner' than black with a small percentage of the other primaries.
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Vector Graphics
Graphics created in programs such as CorelDRAW® where shapes are represented as a series of curves and lines. Vector graphics are also referred to as object-based graphics. This contrasts with bitmap graphics which are created pixel by pixel in paint programs and by scanners.
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Web Offset Press
A printing press that uses paper rolls as opposed to individual paper sheets. This type of press is normally used for high volume publications because of its ability to work at a higher speed than sheet fed presses.
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