Glossary of Terms

Printable version

Additive Colour System

System that adds red, green, and blue light together in varying amounts to produce all colours. Equal amounts of red, green, blue produce white.


Layout, type or pictures that extend beyond the trim marks on a page. Bleeds are required to print an object to the edge of the final, printed piece.

Blends in a PDF (Gradients)

A blend is a gradual transition from one colour or tint to another. Sometimes blends are also referred to as “gradients” or “fountains”. A lot of applications can be used to create such blends. There are also quite a number of ways in which this effect can be achieved. We can make a distinction between the techniques used prior to PostScript 3 and Acrobat 4 and those used after those releases. All of this changed when “smooth shading” and “idiom recognition” made an appearance in Adobe products. Smooth shading is a technique that Adobe introduced in PostScript 3 and PDF 1.3. It is a very fast and compact way of defining blends that look great and output fantasticly, even at fairly low resolutions or high screen rulings. Unfortunately there are still a lot of applications on the market that cannot generate smooth shadings themselves, either because the programmers are too lazy to implement the algorithm or because the programmers want to guarantee compatibility with older non-PostScript 3 RIPs.


Cyan, magenta, yellow, and black. The inks used in colour process printing. Black (K) is usually added to enhance colour and to print a true black. Also, one of the modes used to specify colour in computer graphics.

Colour Separations

The division of a multicolour image into monochrome components for colour printing. Four colour or process separations result in four pieces of film (CMYK); spot colour separations result in one piece of film for each spot colour.


Cutting out an area of an image.

Crossovers (also known as double trucks)

Type or graphic elements that continues from one page across the gutter to the opposite page.


Dots per inch. The measure of resolution at which monitors and printers display text and graphics.


Encapsulated PostScript. A file format used to transfer PostScript information between programs. Resolution independent.


A complete set of characters in a typeface.

Four Colour Process

Printing in full colour using four colour separation and CMYK inks.


For position only.


The inner margin between two facing pages.

Hairline Rule

The thinnest rule that can be printed, thinner than half a point. Never to be used, instead specify 0.25 points.


An illustration reproduced by breaking down the original tone into a pattern of dots of varying size. Light areas have smaller dots and darker areas or shadows have larger dots.

Halftone Screen

A grid of parallel lines used to resolve continuous-tone copy into dots. The number of lines to the inch controls the coarseness of the final dot formation. The screen used depends on the printing process and the paper to be used; the higher the quality the more lines can be used.


Page arrangement for printing on a large sheet, so that the pages are in correct order when the sheet is folded and trimmed to final size.

Line Screen (LPI)

The number of lines or dots per inch on a halftone screen. Also called screen frequency.

Master Pages

Pages that contain elements common to all pages in a publication, such as page number (folio).


A colour matching system that refers to colours by number instead of by name.


A page description language developed by Adobe Systems.

Process Colours

See four colour process.


The measurement of dpi used in typesetting to express the quality of output. The greater the number of dots, the more smooth and cleaner the character/image will be.


Raser Image Processing


Red, green, blue. Generally used for displays on television screens, computer monitors, movie theatres and the internet.


Reducing or enlarging the amount of space an image occupies.

Screen Frequency (LPI)

The number of lines or dots per inch on a halftone screen. Also called line screen.


The darkest area of a photograph or illustration.

Space Junk

Unused elements left on the pasteboard in a page layout program.

Subtractive Colours

The CMYK inks used in process-colour printing to create different colours. In contrast to additive colours (RGB), CMYK inks produce darker colours when combined.