What's the difference
between RGB and CMYK?
How about .gif and .jpg files?
When do you use one or the other?
What do these different extensions mean?
What about some of those newer web terms
such as cascading style sheets,
dithering, and web palette?

 

Below you'll find some answers to these and many other questions.

We've tried to provide some file extension explanations along with design, print and internet terms (with definitions and explanations) that'll hopefully help you maneuver the often confusing corridors of design, printing and the internet.

Also, if you look close enough, you'll also find some of our own definitions with a lighter twist :-)

SOME EXTENSIONS YOU MAY ENCOUNTER . . .

.ai		Adobe Illustrator
.aif/.aiff		Audio AIFF files
.aifc		Compressed AIFF file
.asp		Active Server Page
.au		Audio sound file
.avi		Video file
.bmp		Microsoft bitmapped file
.cfm		Cold Fusion Metafile
.css		Cascading Style Sheet
.dcr/.dir./dxr		Shockwave files
.dll		Dynamic Link Library element
.doc		Microsoft Word text file
.eps		Encapsulated Postscript File (graphic)
.exe		Self extracting file
.fhd		Freehand
.gif		Graphics Interchange Format graphic used primarily on the Web
.gz		Compressed file made by gunzip
.hqx		Mac BinHex Archive
.htm/.html		Hypertext Markup Language file
.jpg/.jpeg		Joint Photographic Expert Group graphic used primarily on the Web
.lib		A Library file
.mid/.midi		Musical Instrument Digital Interface audio file
.mov		QuickTime movie file
.movie		Movie file by Silicon Graphics
.mpg/mpe		Movie
.p65		PageMaker 6.5 file
.pbm		Portable Bitmap Image
.pcd		Kodak photo CD image
.pdf		Portable Document File
.pic		A common graphic image file format
.pl		Perl source file
.png		Portable Network Format graphic used primarily on the Web
.ppt		PowerPoint file
.ps		Postscript file
.pub		Microsoft Publisher file
.qt		QuickTime movie
.qxd		QuarkXPress file
.ra		RealAudio file
.rtx/.rtf		Rich Text Format
.sea		Self extracting Stuffit file
.shtm, shtml		Server-Side Includes
.sit		Stuffit archive
.snd		Digitized sound file
.swf		StuffitShockwave Flash file archive
.tar		A Compressed file
.tif/.tiff		Tagged Image File Format graphic file
.txt		An ASCII text file
.wav		Waveform audio file
.wpd		WordPerfect file
.wrl/.wrz		VRML 3D file
.xll		Excel file by Microsoft
.xml		Extensible Markup Language
.zip		Compressed file expanded by WinZip (PC) or Stuffit (Mac)

.

TERMS AND DEFINTIONS THAT MAY HELP YOU . . .

Adaptive Palette
see "Palette."

Adobe Acrobat
An application program designed to facilitate the creation, viewing and printing of PDF (Portable Document Format) files.

AIFF
Stands for Audio Interchange File Format. Is a standard audio format on both Macs and PCs used to distribute audio information on the web.

Airbrush
A small pressure gun -- either actually or representative in a graphics program (such as Photoshop) that sprays a pigment of varying intensities to obtain graduated tone effects and/or retouching.

Alpha Channel
An extra channel used for storing specific information about a graphic such as transparency or masking properties. Other channels typically store color information.

Analog Color Proof
An off-press color proof produced by separation films.

Animated GIF
GIF files stored and played together in a specific sequence to simulate motion.

Anonymous FTP
The method for retrieving documents using FTP (File Transfer Protocol) which facilitates the sending and receiving of files.

Applet
See "Java Applet."

Archie
Search devices for documents on anonymous FTP servers which attempts to match file names.

ASCII
Stands for "American Standard Code for Information Interchange." Files comprised of alphanumeric characters. Is the standard for character sets. Is limited to 255 characters. Used for text. Binary mode should be used for graphics and multimedia.

AVI
A file format where audio and video are interleaved in each frame for a better presentation.

Bad Break
In text composition, hyphenating a word at an awkward place, ending a paragraph with a single word, or ending a page with a single line of a starting paragraph. Also, awkward line lengths of successive lines.

Binary Files
Files made up of raw data that should be used for graphic and multimedia files. Text files should be transferred as ASCII files.

Bindery
The final phase of the printing process where the printed product is put into its final form such as folding, gluing, stitching, cutting, and binding.

Bit Map
The electronic representation of a page where every part (pixel) is represented by either on (totally black) or off (totally white). Or a map that has bite marks in it :-).

Blanket
The rubber mat on a printing press that transfers the ink from the plate to the product. Or, an item carried by some that purportedly produces security :-).

Bleed
The part of the printed job that extends beyond the borders of the finished trimmed product. Or, the usual result of carelessly chopping vegetables for dinner :-).

Blueline
A proof of the finished job where all colors in the job are represented by different values of blue. The proof is produced from the same film that the finished product will be produced from.

Burn
The term used for exposure of the plate to the light which produces the image. Or the process of slowly becoming angry :-).

Camera Ready
Copy that needs no editing before the photographic process. Or, a term describing a person who appears in a large number of photos from an office party :-).

Cascading Style Sheets
see "CSS."

CD-ROM
Stands for Compact Disc-Read Only Memory.

CGI
Stands for Common Gateway Interface. Is the standard for scripts that helps world wide web browsers communicate with web servers. For example, forms on web pages must use CGI scripts to have the information submitted by customers transferred to owners in usable form. Allows for the user requests to create dynamic web sites.

Client
A computer that receives some sort of assistance from the "server" computer.

Coated
Term used to describe paper that has an outer layer that gives a smooth finish and has a glossier look. Usually produces a sharper dot because ink resides more toward the surface of the paper. Or the state of having a coat on in cold weather :-).

Coating
An outer coating (usually emulsion, lacquer or varnish) applied to the paper or board to protect it.

Collate
A finishing term indicating the placement of individual sheets in a precise order.

Colors
Two popular color modes are RGB and CMYK. RGB stands for red/green/blue. RGB is based on the light spectrum and is the system of color used for Web design, since the finished product is viewed on the computer screen.

Red, green and blue added together produce white light. Black is produced by the absence of all three. Red and green produce yellow. Red and blue produce magenta. Blue and green produce cyan. Different variations of the three colors produce the other colors of the spectrum.

CMYK is the system used for printing presses. Printers mix the appropriate amounts of 4 colors together to produce individualized colors. C stands for cyan, M for magenta, Y for yellow, and K for black. Cyan and magenta produce variations of blue; magenta and yellow produce variations of red; yellow and cyan produce variations of green. All four colors mixed together produce black. Different variations of the colors mixed together produce other colors of the spectrum.

CMYK is also referred to as process color or 4-color.

Another mode is index color. An index color is a color that is "indexed" to the color palette so that the only colors found in the image are those found in the color palette.

A grayscale mode refers to each pixel in the image represented as a shade of black.

A bitmapped mode refers to each pixel in the image represented as either all black (100%) or all white (0% black)

Color Separations
Printed colors are produced by a combination of small dots produced by individual plates. Spot color jobs use one plate of black dots and 1-2 other plates of the individual color(s).

For example, for a 4 color job, each individual part of each color photo/graphic/text part is broken down to the individual CMYK elements. Four plates are produced with the dot patterns needed to produce each color when combined with the others.

Cookie
A marker stored in a file in your hard drive when you visit certain web sites. This marker identifies to the web site that you had previously visited the site. It does not identify you, the individual user, only your computer. It does not reveal your e-mail address, name, or other information, only that you had visited the site previously.

Crop
The process of eliminating parts of a photographic image/graphic that are not needed.

Crop Marks
Printed lines usually at the four corners of a printed page indicating the edge of the paper. Or the marks left in the dirt after pulling out a plant :-).

Curl
The distortion of a sheet due to the differences in the surface coatings of both sides of the sheet or due to moisture from an offset press. Or, the lifting and lowering of a weight involving the arms :-).

Cyan
The "C" of CMYK. See "Color" above.

CMYK
See "Color" above.

CSS
Stands for Cascading Style Sheets. A newer system for controlling the presentation of text, graphics, sound, etc. on the web in addition to HTML.

Custom Palette
See "Palette."

Densitometer
A device used for measuring the degree/quality of density of black produced by an output device (as an imagesetter) or the accurate degree of a screen.

Density
The degree of lightness or darkness of a photographic image (usually of an individual black dot making up the image). Or, the degree of a dull person to understand what is going on :-).

Descender
The part of a lower case letter than descends below the base line. Examples are p,g,y.

DHTML
Stands for Dynamic Hypertext Markup Language. Refers to web pages that have movement or animation and where there's a higher degree of interactivity with the user. This is done through a combination of HTML, JavaScript, the Document Object Model and Cascading Style Sheets (CSS).

Die
A metal object that conforms to the image that it is pressed into. Is used to cut or place the image onto the paper in the finishing process. Is generally used to produce special images.

Digital
The process of transporting text/images into computer language where it can be manipulated, edited and transported into an edited final form.

Dithering
Refers to the remaking of old colors on an image to new colors located only on the palette. The result can be a random speckled or noise pattern.

Document Object Model (DOM)
Refers to the internal hierarchical organizational arrangement of the elements of document. It allows scripts and style sheets to function in the file.

Document Type Definition
See DTD below above.

Dot
The individual components of a halftone.

Dot gain
An expansion of a dot from the press plate to the finished product due to absorption and spreading of the dot on the paper.

Double Burn
Exposing the same place to different images at different burn sessions. Or, the process of really getting angry :-).

DNS
Stands for "Domain Name System." Translates a URL (as http://www.eaglegraphicsprinters.com) into its equivalent IP address.

DPI (dpi)
Dots per inch. Used to describe the number of dots found per linear inch in an image or graphic. It is sometimes incorrectly used in reference to the resolution of a computer screen which should be measured in ppi (pixels per inch).

DTD
Stands for "Document Type Definition." Includes the rules as to how a markup language (such as XML) are applied.

Dummy
A preliminary layout of the placement of text, images and graphics as they are to appear in the final printed piece. Also, what we sometimes feel like when given a task that is beyond our experience and/or expertise :-).

Duotone
A two-color halftone reproduction from a one color photographic/image.

Dylux
See blueline above.

Dynamic web site
A site whose content changes based upon user requests and content stored and requested from the server.

Embossing
Performed by pressing a die or object against the paper product causing the paper to conform to the image on the die or object

Emulsion
A light sensitive coating found on photographic film. Or, the process of totally being absorbed in a four course meal. :-)

Exact Palette
See "Palette."

Flaming
Generally the result of spamming (see below). When a large number of unsolicited messages are e-mailed randomly, large numbers of retaliatory messages can be returned to the spammer to deter this activity.

FTP
Stands for File Transfer Protocol, one of the main parts of the internet along with the world wide web, e-mail, gopher, usenet and telnet. Is used in the sending and receiving of files.

Flat
A number of negatives taped to materials ready for platemaking.

Folio
A page number.

Font
The complete assortment of letters, numbers, punctuation, etc. that belong to a particular design family. For example, the Times, Arial or Helvetica fonts.

Format
The different elements of the printed product such as margins, page size, indentation, space between lines, etc.

Gamma
Refers to the brightness of a computer screen. For example, the gamma of a Mac screen is usually set to 1.8 whereas the brightness of a PC screen is usually 2.5. Therefore, images generally appear darker on a PC screen than they do on a Mac screen.

GIF
Graphic Interchange Format. The common format for Web page graphics. Is an 8 bit image (can contain 256 colors) and is used mostly for images that have flat color and sharp images such as logos, icons, illustrations and line art. Uses LZW lossless compression. Not particularly good for photographic images because all colors are reduced to a maximum of 256 colors. Photographic images are better stored in a .jpg format.

Gopher
A main, but less used, part of the internet. Is used to locate and retrieve resources on the internet. Or, an irritating animal that only eats one's most favorite plants and vegetables in a garden. Or, a person regularly sent to buy coffee and/or donuts for the office :-).

Gripper Margin
The space from the printing area to the edge of the paper where the metal fingers of the printing press clamp on to the paper to pull it along which is usually about half an inch. Or, the space around a bowl or bag of M & Ms beyond the full extension of one's arm and hand :-).

Gutter
The blank space between the printing area and the binding.

Hard Copy
The visual representation of output in printed form sent from a computer or printer. This is in contrast with the copy seen on a computer screen.

Hexadecimal
The base 16 number system used on the world wide web to specify RGB colors. The elements consist of 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F (where A through F represent the numbers 10 through 15).

HTML
Stands for Hypertext Markup Language. Is the language of the World Wide Web. All documents on the web are written in HTML which are read by web browsers.

HTTP
Stands for Hypertext Transfer Protocol. Is the international standard used by world wide web browsers to send and receive files over the internet. Most domain names start with the http:// prefix.

HTTPS
Stands for Hypertext Transfer Protocol Secure. Is the secure version of HTTP (see above.) Uses certificates that can identify the server and client and encrypts all information between them.

IIS
Stands for "Internet Information Server". Is the software included with Windows NT that interfaces with other services on the system.

Imagemap
An image that has hypertext links to other sources associated with different parts of the image.

Index Color
A color that is "indexed" to the color palette so that the only colors found in the image are those found in the color palette. See "Colors"

Indicia
Postal information placed on the printed product.

Interlacing
A process performed on a .gif image file on the Web that will cause it to appear gradually in 4 passes rather than all at once but later. The first pass shows 12.5% of the image, the second 25%, the third 50% and the fourth 100%.

IP Address
Internet Protocol Address. Defines the location of any computer on the internet. The address consists of 4 numbers ranging from 1 to 256 such as 231.34.83.167. Every computer connected directly to the internet (as an internet service provider (ISP)) has an IP address.

IRC
Internet Relay Chat. Offer public and private places "rooms" where different people can meet and type messages to one another.

Java
A programming language whose main contribution to the web is Java applets which are small, executable programs. Not to be confused with JavaScript which is entirely different. Or, a definite need of many people before they can think clearly in the morning :-).

Java Applet
A small, executable program that is created in the Java programming language.

Java Server Pages (JSP)
Programming on the server that combines HTML and Java to produce dynamic web pages.

JavaScript
A scripting language residing on a client computer that adds interactivity to a web page. It is distinct from the Java programming language.

JPEG
Stands for Joint Photographic Experts Group. Also known as jpg. An efficient method for compressing photographic images for use on the world wide web or for images that have gradations and no sharp edges. Jpeg files use lossy compression.

Kerning
The process or subtracting space between two letters. Or, the process of making popcorn :-).

Lacquer
A clear coating that is applied to a printed page for appearance and/or protection, usually containing a resin or solvent.

Lamination
A plastic coating applied by heat to a surface for protection and/or appearance.

Leading
The amount of space between lines of print.

Lines per inch (lpi)
The number of lines per inch that a printing press is able to print at. This determines the amount of sharpness and detail capability of the press. Newspaper presses may only print at 60-80 lpi, while some four color process printers can print at over 200 lpi.

Linux
A newer, free operating system known for reliability and performance, developed by Linus Torvalds.

Lossless Compression
A compression where no image information is lost in the compression process. The resultant image is identical to before the compression as in a gif file which uses lossless LZW compression. This is in contrast to "lossy" compression (as in a .jpg file) where the resultant image is much smaller but has lost image information. However, the resultant loss if often undetectable in the image.

Lossy Compression
See "Lossless Compression" above.

LZW compression
Stands for Lempel-Zev-Welch. A compression used in tif and gif files that takes advantage of similar pixels (as flat colors) located side by side. LZW compression can take a larger similar area and store in a reduced formula. For example, a row of 25 green pixels can be stored as "25 green."

Magenta
See "Colors."

Masking
A configuration of any sort that prevents part of an image from showing. A mask could be used to show an image only through letters of a word or phrase. Or the process of preparation used by many children as they prepare to go trick-or-treating :-).

MIDI
Stands for Musical Instrument Digital Interface. A file format that contains a set of mathematical commands rather than audio information. Are very compact so large amount of musical information can be stored in a very small area. Are only used for notes, not real sounds, so the human voice could not be reproduced in this type of file.

Moderated
A newsgroup or an e-mail list where all the posted messages are first approved by a moderator. The purpose of a moderated group is to keep the discussion on a certain subject or topic and to prevent non pertinent messages (including spam) from being posted.

Moire
Undesirable screen patterns produced from CMYK plates. They are usually produced from overlapping halftones scanned at the wrong screen angles.

Negative
Usually refers to photographic film where light values are reversed -- dark areas are light and light areas are dark. Or, the attitude one can attain when having a bad day :-).

Netiquette
The guidelines as to how internet participants should participate with one another.

ODBC
Stands for "Open Database Connectivity." Allows for access to database sources.

Opacity
The amount of light that is able to penetrate to the finished object. A 80% opacity means only 80% of the original source has penetrated.

Opaque
To prevent an area from printing on a negative by applying a paint or tape that will not allow light to penetrate.

Overrun
The number of copies printed over the specified quantity. Or, the feeling one can have when beset with too many responsibilities at the same time :-).

Palette
The series of colors used in an application (such as Photoshop).

An "adaptive palette" adapts all the colors in a image to conform to the colors in the palette.

An image in "index color" mode will "index" all the colors in the image to those found in the palette. In other words, the palette will now only contain colors found in the image.

An "exact palette" will contain only the "exact" colors found in the image.

A "system palette" contains the colors defined by each (Mac/Windows) operating system and will cause those colors to be used in the image.

A "uniform palette" contains an even sampling of colors from the RGB spectrum.

A "custom palette" allows you to use a previously user defined palette that was saved and apply it to the image.

A "web palette" contains only those colors that are web safe. Certain application programs (such as Photoshop 4 and 5) come equipped with it.

Pass
In printing, the number of times the paper must go through the press to print the final product. Printing in one pass means all colors are printed at one time. Printing in two passes means the paper must pass through the press two times to lay down all the ink needed for the product. Or, the response you want to give when your boss gives you accounts or jobs that you cannot handle :-).

PDF (Portable Document Format) files
Document format that retains the font and graphic information of the original. PDF files can be printed using Adobe Acrobat Reader and retain the accurate font and graphic representation of the original. PDF files can be made from within such applications as PageMaker and QuarkXpress.

PHP
Stands for "Personal Home Pages." A server side script (like ASP and Cold Fusion) that allows for the production of customized dynamic web pages.

Pica
A typographical unit, representing 1/6 of an inch.

PMS Colors
Stands for Pantone Matching System colors. An international color language developed by the Pantone Corporation that is used for the identification and control of color. Every color is represented by a name or a number. Is the most widely used system to identify "spot colors."

PNG
Stands for Portable Network Format. A newer graphics file format that offers high quality images on the web, but has little browser support from Netscape Navigator 4.x and Internet Explorer 4.x.

Point
A typographical unit, representing 1/72 of an inch. There are 12 points in a pica.

Porous
A word used to describe the ability of a stock to absorb ink. Examples are newspaper and cardboard that give a dull image where details can be lost.

Positive
Usually refers to photographic film where light and dark values are the same as on the original. See "negative" above.

PostScript
The operating system language through which desktop page systems operate.

PPI
Pixels per inch. Is the resolution that an image will be displayed on a computer screen. For example, a one inch image that has a resolution of 72 pixels per inch will be one inch long on a computer screen that has a resolution of 72 pixels per inch. On a computer screen that has a higher resolution such as 100 pixels per inch, the image will display smaller than one inch.

PPP
Point-to-Point Protocol. Is a standard that allows desktop computers to connect to their internet service provider and the internet through their modem and standard telephone lines.

Process Color
Also referred to as a 4-color process. Every color is represented as a combination of cyan, magenta, yellow and black. All colors are printed from 4 photographic plates. Each plate prints a pattern of small dots that when combined with the other plates produces the desired color.

QuickTime
A file format that makes it possible to view audio and video information on a computer. Or, the speed at which a clock moves during breaks and lunch :-).

Registration
The process of printing each plate in a multicolor job in exactly the correct alignment so they fit together exactly. The correct alignment is determined by "registration marks" located outside the margins of the printed product.

Saddle Stitch
The binding of a booklet at its fold with one or more staples. Or, how a riding-challenged cowboy keeps his saddle together :-).

Sans Serif
In typography, fonts that do not contain the small terminating strokes at the tops and bottoms of the letters. Examples of sans serif typefaces would be Helvetica, Arial and Avante Garde.(see also serif)

Scanning
The process of converting original artwork such as images/photos/graphics/ into digital information by means of a scanner that can be enlarged, edited or retouched on a computer using application programs.

Score
To impress a rule on the printed product to make folding easier.

Serif
In typography, fonts that contain the small terminating strokes at the tops and bottoms of the letters. Serif fonts are used mostly for body text because they are easier to read. Examples are Times and Palatino. (see also sans serif)

Server
A computer that provides some sort of assistance to a "client" computer. Or, generally a newer employee who is asked or expected to help more established employees with their work :-).

SGML
Stands for Standard Generalized Markup Language. A language that provides a series of rules for the structure of an internet document. HTML is a subset of SGML.

Side Stitch
The binding of printed materials by a staple along one side of sheet

Signature
The name given to a printed sheet which usually comes in configurations of 4, 8, 16, 32 or 64 pages.

SLIP
Stands for Serial Line Internet Protocol. Is a protocol similar to PPP that allows desktop computers to connect to their internet service provider and the internet through their modem and standard telephone lines.

SQL
Stands for "Structured Query Language". Is a standard language that allows for accessing specific information in a relational database.

Spamming
A practice of sending unwanted or unsolicited messages to large groups of people, generally of an advertising nature.

Spine
The edge upon which a booklet or publication is bound.

Spoilage
The amount of planned paper waste from a job.

Spot Color
Single color (other than black) used in a printed piece. Is usually a customized ink coming from a PMS system. Or, the result of dropping part of our lunch or snack on our laps :-).

Spreads
Also called trapping on a digital system. The slight overprinting of one image upon another to prevent fringes or halos caused by slight misalignment of plates. Or, what happens to our waistlines if we eat too much or exercise too little :-).

Stet
A proofreaders' mark indicating the copy should remain as it was.

Stock
The paper or other material that is to be printed upon.

Stripping
The positioning of photographic negatives or positives on a flat to prepare it for the platemaking process.

System Palette
See "Palette."

Telnet
One of the main parts of the internet that allows users to log into a computer from a distance location. Specifically an internet protocol.

Trapping
See "Spreads."

Trim Marks
Marks (such as registration marks) placed on the printed product to indicate where the edges of the final product are.

Uncoated
A quality of paper that does not have an outer coating (such as emulsion, lacquer or varnish) to protect it.

Uniform palette
See "Palette."

Up
Refers to the number of exact duplicates of the same job that will be printed on a larger sheet to prevent waste of paper. For example, many business cards are printed 4-up, that is four at a time on the same paper, and then cut individually.

URL
Stands for Uniform Resource Locator. The unique address of every resource located on the internet.

Usenet
One of the main parts of the internet that contains a collection of thousands of newsgroups named according to topic. One can place e-mail messages in an appropriate group, to which others can respond in kind.

Varnish
A thin, protective layer that is applied to the printed product for protection and/or appearance.

VRML
Stands for "Virtual Reality Modelling Language." A standardized language that allows for the production of moving 3-D effects within a HTML document.

Web Palette
See "Palette."

XML
Refers to "Extensible Markup Language." Is a newer standard for the markup of pages on the web that contains features not available to HTML.

XSL
Stands for "Extensible Stylesheet Language." Contains the rules of style that will be applied to a corresponding XML document.

Yellow
One of the primary colors in CMYK. See "Colors."