Print & Design Glossary

Bitmap

The term "bitmap" has two distinct meanings:
1) It can refer to an image's colour mode. A bitmap is a black and white image - with no intermediate shades of grey. (See image below, far right).

Colour Modes
CMYK (32-bit)	RGB (24-bit)	Greyscale (8-bit)	Bitmap (1-bit)

2) A bitmap is also an image type. A bitmap image is made up of pixels and its clarity depends on the resolution and size at which it is printed. (See our File Formats page for more information.) The colour mode of a bitmap image can be Bitmap (1-bit), Grayscale (8-bit), Index (8-bit), RGB (24-bit), or CMYK (32-bit) color mode. The higher the "bit depth", the larger the file size will be. (E.g. the file size of an RGB or CMYK image is larger than that of a greyscale image). A bitmap image can also be called a raster image.

Bleed

The design goes right to the edge of the paper. The job is designed and printed larger than needed, then trimmed to the finished size. See an example of a design that bleeds.

CMYK

Cyan Magenta Yellow Black - the four ink colours used in full-colour printing. They are also known as "process colours".

dpi

dots per inch. The 'dot' of dots per inch describes the smallest dot that a printer can produce. To create a half-tone effect, a printer varies the amount of ink it puts on the paper. Lots of ink makes a strong colour; a little ink leaves a lighter colour (more of the paper colour shows through). The printer does this by varying the size of the halftone dot in a half-tone grid measured in 'lpi'. A normal 'half-tone' dot is made up from a framework of these smaller 'printer' dots. So 'dpi' measures the smallest size of these 'printer' dots. We print at 2400dpi for high quality output.

duotone

A tonal image (such as a photograph) is changed from greyscale mode to duotone mode (which has two colour channels) in a program such as Photoshop. Each channel is assigned a spot colour. This gives the image more depth than if it were printed in a single colour as part of a spot colour print job. The file must be saved in the .eps file format.

EPS

Encapsulated Post Script. An image file format made from multiple objects, which uses the principals of PostScript code. Because of this, a vector EPS can be reduced or enlarged to any size without losing quality. EPS files can also include bitmap images. Spot color duotones, tritones and quadtones in Photoshop can only be saved in an EPS format.

greyscale

A colour mode made up of 256 shades of grey, including white and black. If a logo or drawing is made up of shades of grey, it is a greyscale image. If a logo or drawing is made up of black and white lines, then it is a bitmap image.

 

Greyscale

Bitmap

hairline

The thinnest (finest) line that can be created by a printer or platemaker. This varies between machines. Although a hairline can be seen on a printing plate, it is often too fine to hold any ink. It is best to avoid using hairlines - use lines of 0.3 points or thicker.

lpi

lines per inch - describes printer resolution (or "linescreen") by the number of half-tone lines per inch (lpi) that the printer can output - we output at 150lpi. (Higher lpi means higher quality printed output. Newsprint is typically 85lpi.)

PMS

Pantone Matching System®. A widely-used system for specifying, mixing and matching printers' inks.

ppi

pixels per inch. The number of pixels per linear inch of an image file (from a computer, camera or scanner) when stored electronically.

PPI

Printed Postage Impression. A graphic device used on envelopes, postcards and mailing labels to indicate that a business has a Business Reply License. (See our Envelopes page for examples.)

Process colours

See CMYK.

Raster

An image file format (eg. jpeg, gif, tif, psd) made up of pixels, whose color and location on a grid determine the image's appearance. These images are resolution dependent: i.e. they show jagged edges when magnified or printed at a higher resolution than what they were created for. Programs like Photoshop, PhotoPaint and PaintShop Pro produce raster images. Also called a Bitmap image.

RGB

Red Green Blue - the colours that combine to make up all the colours displayed on a computer or television screen.

Spot Colour

Individual colours used in one, two or three-colour jobs are known as spot colours. They are specified accurately by using the Pantone Matching System (PMS).

Vector

An image file format (eg. png, ai, eps, ps, cdr, wmf) that can be enlarged to any size with no loss of quality, because the shapes within it are described by mathematical objects called vectors (vectors). These images are resolution independent and print at the highest resolution available on any given output device. Vector graphics enlarge well and are good at reproducing crisp outlines and details.

Download the full (pdf) version of Admiral's Artwork Guide.
(Right-click and select "Save Target As" to save a copy to your hard drive.)

© Admiral Printers Ltd 2009. Trading as Admiral Design and Print, Wellingborough, Northants, East Midlands.