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EAC Decision on Request for Interpretation 2016-01

(Display Pixel Pitch)

Voluntary Voting System Guidelines 1.1, Volume I, Section 3.2.5.a.iv 

Date: 

June 28, 2016

Questions:

1. What minimum display pixel pitch must a manufacturer use to the meet the 

requirement of Section 3.2.5?

2. Is the standard absolute or can allowances be made similar to those set forth in EAC 

Decision on Request for Interpretation 2015-04 (Visual Display Characteristics; Minimal 

display area).

Section(s) of Guidelines:

3.2.5 Visual display characteristics 

The requirements of this section are designed to minimize perceptual difficulties for the voter. 

Some of these requirements are designed to assist voters with poor reading vision. These are 

voters who might have some difficulty in reading normal text, but are not typically classified as 

having a visual disability and thus might not be inclined to use the Acc-VS. 

a. If the voting system uses an electronic display screen as the primary visual interface for the 

voter, the display shall have the following characteristics: 

i. Flicker frequency NOT between 2 Hz and 55 Hz. 

ii. Minimum display brightness: 130 cd/m2 

iii. Minimum display darkroom 7×7 checkerboard contrast: 150:1 

iv. Minimum display pixel pitch: 85 pixels/inch (0.3 mm/pixel) 

v. Minimum display area 700 cm2 

vi. Antiglare screen surface that shows no distinct virtual image of a light source 

vii. Minimum uniform diffuse ambient contrast ratio for 500 lx luminance: 10:1 
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Discussion:

As stated in the standard, the high level requirement for visual display characteristics is meant 

to “minimize perceptual difficulties for the voter”. One way to improve the readability of a 

display is to make the display larger, thus making the same content larger. This was the intent 

of 3.2.5.a.v and is consistent with comments made in RFI 2015-04 that say that “larger screens 

make the visual display easier to read and navigate.” However, this idea appears to be in 

conflict with 3.2.5.a.iv in that the display pixel pitch requires a higher resolution screen when 

the display size is increased. An example would be a scenario in which content that meets all 

usability and accessibility requirements on a 24 inch 1080p resolution screen could not meet 

the standard if displayed on a 1080p 32 inch screen, even though the content is larger. To 

provide the pixel density required by the standard for the larger displays now available, the 

resolution of the screens at the various display sizes requires the use of products that are either 

not expected to be available on the market for the desired lifetime of a voting system or are 

prohibitively expensive. 

Conclusion:

Similar to the guidance that was given for display size, larger screens that can be shown to 

provide acceptable usability and accessibility will not be strictly held to the 85 pixels/inch 

requirement if the product has undergone thorough usability testing and the submitted 

usability test reports demonstrate good usability and accessibility performance (in particular, 

works for low literacy, low vision, and dexterity). In these cases, EAC will have the reports 

evaluated by usability/human factors experts to confirm the findings in the manufacturer 

submitted usability test report(s).

Effective Date: 

Effective immediately for all new test campaigns.