and Symbol Size
size is one of the most important determinants of text legibility
in any display, but especially with electronic displays. On computer
monitors, characters are formed by small dots or pixels and are
inherently less crisp and distinguishable than print on paper. Optimum
character size depends on the user's position relative to the display
in terms of visual angle and viewing distance.
Angle, Viewing Distance, and Character Size Calculation - These
parameters can be measured and calculated using simple algebra.
Visual angle (A) is defined in degrees. The size
of the visual angle depends on the size of the object being viewed
(H) and its distance (D) from
or Critical Display Elements
and symbols should subtend at least 20 arcminutes.
is 20-22 arcminutes.
a rough estimate, character size should be 1/200th of viewing
Legibility begins to decrease with symbol heights less than
Avoid symbols that subtend less than 16 arcminutes.