This standard establishes ergonomic image quality requirements for the design and evaluation of flat panel displays, defines terms needed to address image quality on flat panel displays, specifies methods of determining image quality on flat panel displays and establishes ergonomic principles for guiding these requirements. This document specifies guiding principles and design requirements. Visual ergonomic requirements are visual comfort, muscular comfort and user acceptability. It also includes the legibility in the presence of ambient room light and the acceptability of unwanted reflected images on flat panel displays. This part of ISO 13406 is applicable to flat panel display screens when used to perform office tasks, to flat panel display screens that consist of a regular array of picture elements arranged in evenly spaced rows without built-in gaps, to the presentation of fonts based on Latin-, Cyrillic- and Greek-origin alphabetic characters and Arabic numerals on flat panel display screens, to the presentation of Asian characters and to flat panel display screens that are large enough to display at least 40 Latin-origin characters. The legibility of flat panels is a principal concern.