Letter Readability

For easiest legibility at a distance, the research indicates that the width of a letter's vertical strokes should be about one-fifth its height. Horizontal strokes may be slightly thinner. These proportions apply equally to capital and lower-case letters.
 

Letter Spacing - The legibility problem created by tight letter spacing is compounded when copy lines are viewed from an angle, which can occur in Outdoor. Notice how crowding can confuse the intention of the copy by causing certain letters to attach visually to adjacent letters, thus "clear morn" could be interpreted as "dear mom."

Line Spacing - As in the case of letter spacing, adequate line space is necessary for maximum legibility. If a copy line is riding "piggyback" on the copy line below it, the interplay of descenders and ascenders creates confusion

Stacking - This reduces readability and is not recommended for Outdoor design. With a single horizontal line of copy, the eye moves through the message rapidly and without interruption. The stacking of additional lines reduces this facility and increases the time needed to comprehend the message. If, however, stacking is necessary for layout purposes, give careful consideration to line spacing.

Upper and lower case type are a lot clearer from a distance and easier to read than all uppercase letters.

Common Mistakes

Crowding too many letters into a space tends to repel the eye and thus defeats the objective of getting type as large as possible.

Strokes which are too fine fade into the background and become invisible at a distance.

Bulky typefaces become blobs at a distance, basic shapes cannot be distinguished, and letters are not recognizable.

Script and similar styles sacrifice the letters basic shape for the decorative aspect, and therefore individual letters cannot be identified.