Glossary of Terms

Laser

Light Amplification by Stimulated Emission of Radiation. Not the lead underpants sort of radiation, it's normally visible or near-visible wavelengths of light. Lasers in print are used as a source of intense, coherent light for exposing film, printing plates or screen mesh emulsions, or in laser printers and some digital presses as a way of discharging static charge to create image areas on photoelectric drums.

Laser printer

A non impact computer printer. It uses a laser to dissipate an electrostatic charge in specific areas of a light-sensitive drum, which then picks up toner by electrostatic attraction. The toner is then transferred to a sheet of paper to form an image which is fused into place by heat and pressure. Related but now obsolete analogue photocopiers use much the same process, but with reflected and focussed light bounced off the original that is being copied.

Latex ink

A water based inkjet ink suitable for outdoor signage, with similar applications and lifetime to eco solvent inks. Currently supplied by HP, Mimaki and Ricoh. It contains resins (called co-polymers) and pigments held in an emulsion in water. Despite the name, it is nothing to do with latex rubber. Latex is the US term for what in the UK is called an emulsion paint, and latex ink is a similar idea to the latter.

LED

Stands for light-emitting diode. A very efficient solid-state lighting technology that is increasingly replacing older technologies across a range of applications from domestic lighting through to UV ink curing. Red, green and blue LEDs are used to create variable colour lighting and sometimes exposure systems for film. Infra Red emitting LEDs are commonly used in remote controls for home entertainment systems.

LPI

Lines per inch. A term mainly used by offset printers to measure the fineness of a regular halftone screen. Most magazines are printed with 175 lpi screens. Inkjet screening works differently, especially with multiple passes, so the dot pitches don't exactly correlate with offset screens.