A "rule-of-thumb" is that each inch of letter height can be seen from 50 feet away. Much depends upon the size of the building, the angle at which you approach the sign, the lighting and, even, the age and visual acuity of the viewer. An airport, parking garage or convention centre needs larger letters than a sign used in a narrow hallway. Also, the headline should be larger – whereas the remaining explanatory text may be smaller. The top row leads you to the sign; once there, you can study the remaining text.
In the sign market, sign legibility is increasingly a "hot button" as our population gets older. Signs read by older individuals need to be bigger and to have better lighting than those read by younger individuals. As vision deteriorates, the letters start to fill in and blur. Recently developed type fonts, however, are designed to have a highly legible lower case alphabet. The research finds that a high X value and letters with a 1:5.7 stroke width to height ratio are more legible. The X value of a font is the height of the lower case letter in proportion to the capital letter. Most sans serif type fonts have an x-height that varies from 73% to 75%. Helvetica has a 75% x-height. A serif font, such as Times, has only a 63% x-height. Researchers have found that your eyes scan across the x-heights of the letters when you read a word. |
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To assist you in making your sign more effective, see "Visual Considerations" at right. |
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