Q is a measure of the ratio of pixels per halftone screen ruling. A factor of 2 would require a scanning 2 pixels per screen line.

A standard keyboard layout based on the American standard typewriter. (Named for the top left row of letter keys.)

For imaging use, visible light, infrared, and ultra-violet. In the broad sense it includes everything from gamma rays to radio waves.

An image that is defined as a collection of pixels arranged in a rectangular array of lines of dots or pixels. See "Bitmap."

A thin horizontal strip across an image. Raster lines are captured one at a time by the scanner. When displayed or printed in sequence, raster lines make up the image.

Changing vector-type image information to raster image information.

Type that has rough or stair-stepped edges. The type does not appear smooth because it has been rendered at a resolution that is too low.

The process of removing ink and stencil from a screen to enable that screen to be reused.

The fraction of the light incident on a surface that is reflected and varies according to the wavelength distribution of the light.

Mirror-like reflectance. The magnitude of the specular reflectance on glossy materials depends on the angle and on the scattering of the light by an uneven surface.

Reflectance of radiant flux reflected at all angles from the surface, thus including both diffuse and specular reflectances.

An instrument that measures the amount of light reflected from the surface of a substrate, referenced against the amount of incident light, reflection density is the inverse log10 of the reflectance, the angle of illumination, and the sensing area specified as 90°, 45° respectively.

Refers to print material that is viewed with the light on the same side of the image as the viewer.

The ability to reflect light or other radiation from the electromagnetic spectrum. These materials can be an ink, coating or a substrate.

The colour to colour relationship in a printed image. The quality of the printed image depends on the accuracy of the registration.

The tackiness remaining in a film which, although set, does not reach the really tack-free stage.

A solid (or semi-solid) which can be dissolved to a liquid state, suspended in a vehicle to make an ink or coating and which, upon drying, forms the solid part of printed film along with the pigment, binder and other materials. Effectively the glue of the ink.

The particular pixel density of an image, or the number of dots per inch a device is capable of recognising or producing. See "DPI" and "PPI."

See "Thinner". An additive used in screen printing to slow the rate of drying in an ink.

Defect in which the ink film recedes in large areas due to incompatibility of the surface energy of ink and substrate.

Removing imperfections or unwanted portions of an image.

The ability of an overprint to re-soften the underlying colour.

A colour model using red, green, and blue; the additive primary colours. Video display systems use RGB data to create screen images.

A process using mathematical algorithms to manipulate and print an image. Also, this software often includes "add-on" features, such as colour-calibration software, various pattern selections, tools or a print-instruction screen.

The pattern created in a colour halftone by the placement of dots of different hues.

The ability of an ink to resist being transferred onto the surface which rubs against it (scuffing, polishing).

The term used to describe the total number of prints produced for a specific job.

An indication of flatness of a surface. Used in screen printing to indicate the flatness of the print side of the stencil.