The Effect of Font Size on Readability
Outdoor art designers use the scale on the right to determine the actual height of the lettering on a billboard. The most important information in the copy should be the largest to ensure it is read first. How Distance Influences Read
The image below shows how letter sizes will appear from 500 feet away and simulates a billboard on a freeway. Which sizes can you read best? 
The image below shows how letter sizes will appear from 300 feet away and simulates a billboard on a highway. Surface street billboards allow the smallest font size. Common Letter Size Pitfalls in Outdoor Design
The Magazine Ad: Print advertising can utilize the “white space rule” which allows open space for visual effect. The same style of ad becomes a challenge to read at billboard scale. 
Excessive Copy: The temptation to include too much information forces the use of small letter sizes resulting in unreadable text and a confusing message. The outdoor rule of thumb is “Seven Words or Less”. |
