Georgia Tech Research Institute
 
Issues

Displays: Issue 4 of 6

Issue: Small text and icons are difficult for users with low vision to perceive.

A museum kiosk shows a display that allows the user to select a category of information to view.  The text on the screen is very small, and the icons representing the three categories are also very small.

Text and icons on GUI displays may be difficult for some users to read if they are too small.

Populations Impacted: Users with low vision.

Potential Solutions:
  • Ensure that the font size of the text is sufficiently large. For 20/20 vision, the Human Factors Design Standard (HFDS) recommends that the height of characters occupy a visual angle of 16 to 24 minutes of arc. To compute the character height, use the following formula

    h = 2dTan(x/2)


    where h is the character height, d is the viewing distance, and x is the desired angle in radians. (One radian equals 3437.747 arc minutes, or 57.296 arc degrees.)

    1194.31(b) of Section 508 states that a mode that does not require visual acuity greater than 20/70 must be provided. Multiplying the character height (h) calculated for 20/20 vision by 3.5 (70/20) yields the recommended character height for 20/70 vision for the specified viewing distance.

    While this font size may not be possible for all on-screen text (including control labels, user instructions, and other textual information), making the text as large as possible will increase the chance that users with low vision will able to read the text.

  • A museum kiosk shows a display that allows the user to select a category of information to viwe.  The text on the screen is large, and the icons representing the three categories are also large.
  • Ensure that icons are large enough for low vision users to see. The largest dimension (height or width) of icons should be at least as large as the character height calculated above. Icons should be made as large as possible, given the space available.

  • Provide contrast adjustment for the display. Although users with low vision prefer and generally require larger fonts, they may be able to read smaller fonts if the contrast is sufficiently high. Provide a range of contrast settings for the user to adjust through a hardware control. (Software controls are problematic, because if the contrast is insufficient for the user, the user may not be able to read the display in order to find the contrast adjustment controls.)

  • Provide an alternate display mode with larger fonts and high contrast options. A user-selectable alternate display mode that uses larger fonts and provides high contrast options, even if it contains only the most important information and controls, will be useful for users with low vision.

  • Provide alternatives to the visual display to facilitate interaction by users with low vision. A voice display could be integrated into the device, so that visual content is presented in an auditory fashion as well. For example, using a set of hardware controls, the user could navigate through configuration menus that are voiced, without having to read the menus on the display.

Applicable Guidelines:
ADA-ABA - 707.5
Section 508 - 1194.31(b)
Section 255 - 1193.43(b)
HFDS - 5.11.1, 5.11.7, 8.2.5.6.5, 8.2.5.6.6, 8.2.5.6.9, 8.18.3.1
EITAAC - 5.2.1.2.2