making text legible - baltimore (wdcb) chapter

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Making Text LegibleDesigning for People with PartialSightby Aries Arditi, Ph.D

Here are basic guidelines for making effective legibilitychoices that work for nearly everyone.

How does impaired vision affect reading?

Impaired vision often makes reading difficult by:

Reducing the amount of light that enters the eye

Blurring the retinal image

Damaging the central portion of the retina best suited toreading

Light reduction and blurring reduce the effective contrast of thetext, while central retinal damage impairs the ability to see smallprint and to make eye movements that are crucial to reading.

1. ContrastText should be printed with the highest possible contrast. There isgood evidence that for many readers who are older or partiallysighted, light (white or light yellow) letters on a dark (black)background are more readable than dark letters on a light

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simulation of acataract.

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background. However, the traditional dark on light may beaesthetically preferable.

2. Type ColorVery high contrasts are difficult to achieve with color combinationsother than black and white. Printed material, generally, is mostreadable in black and white. Different colors may be important foraesthetic or other reasons, but it is better to use suchcombinations only for larger or highlighted text, such as headlinesand titles.

3. Point Size


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Type should be large, preferably at least 16 to 18 points, but keepin mind that the relationship between readability and point sizediffers somewhat among typefaces.

4. LeadingLeading, or spacing between lines of text, should be at least 25 to30 percent of the point size. This is because many people withpartial sight have difficulty finding the beginning of the next linewhile reading.

5. Font FamilyAvoid complicated, decorative or cursive fonts and, when they


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must be used, reserve them for emphasis only. Standard serif orsans-serif fonts, with familiar, easily recognizable characters arebest. Also, there is some evidence that sans-serif fonts are morelegible when character size is small relative to the reader's visualacuity.

6. Font StyleWhile there is little reliable information on the comparativelegibility of typefaces, there is some evidence that a romantypeface, using upper and lower cases, is more readable thanitalics, oblique or condensed.

7. Letter SpacingText with close letter spacing often presents difficulties for readerswho are partially sighted, especially those with central visual field


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defects. Where possible, spacing should be wide. Monospaced fontsrather than proportionally spaced fonts seem to be more legible forthese readers.

8. MarginsExtra-wide binding margins are especially helpful in bound materialbecause it makes it easier to hold the volume flat. Spiral bindingcan be helpful as well. Many visual devices, such as stand- andvideo-magnifiers, are easiest to use on a flat surface.

9. Paper FinishPaper with a glossy finish can lessen legibility because manypeople who are older or who have partial sight also have problems


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with glare.

10. DistinctivenessVisual impairment often makes it difficult to find a book or otherdocument that is buried among similar publications, especially forsets with volumes that differ only in title or number. Use ofdistinctive colors, sizes and formats on the covers can be especiallyhelpful to older individuals and those who are partially sighted.

Designers can help to compensate for the difficulty experienced byreaders who are partially sighted by following the guidelines in thisbrochure.

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