Specular Reflection and Usability of Tablet PCs

1. Specular Reflection and Usability of Tablet PCs My eyes! Nooooo! It burns! John GoreCOMP 7700Spring 2006

2. Outline • Introduction • Specular Reflection • Experiment Design • Demonstration • Results • Conclusions

3. Introduction The purpose of this study is to test the effects of Specular Reflection on Tablet PC… • Reading Speed • Input Speed • Usability This study was performedby Auburn Engineers (www.auburnengineers.com)

4. Specular Reflection • Specular Reflection occurs when light bounces off a smooth surface into an observer’s eyes. For this to occur, the angle between the observer’s eyes and the surface and the light source and surface must be the same. • How can we avoid specular reflection? Change the geometric relationship. • Tilt the Tablet • Change Posture • Move Light Source

5. Experiment – Conditions • Display Quality • Narrow vs. Wide: Type of filter used on the Tablet PC screen • Low Ambient vs. High Ambient light: 30 foot-candles or 105 foot-candles • High Reflectivity vs. Low Reflectivity: Type of Tablet PC screen cover • Tilt Angle: 0, 30, 45, 60 degrees

6. Experiment – Tests • Chapman-Cook Speed of Reading Test • Given a passage such as “There was a fire last night and five houses burned to the ground. It all happened because someone was careless and threw a nail into the waste-paper basket,” pick the inconsistent word • 6 passages per test • 4 options per passage

7. Experiment – Tests • Target Tap Test • Based off of Fitts’ law and ISO input testing specifications • 4 circles of varying radiuses • 6 sequential targets positioned along the circumference of each circle • Targets separated by 190 degrees

8. Experiment – Tests • Questionnaire • 7 point Likert scale • Strongly Agree to Strongly Disagree • 7 Questions such as “I can quickly tap targets with the stylus when using the Tablet PC” • Interview • “Is tilt condition X acceptable?” • “Rank the tilt conditions in order of preference” • “Do you prefer Wide or Narrow?”

9. Demonstration

10. Results – Display Quality Speed of Reading Test • Best overall condition: Narrow, Low Ambient, Low Reflectivity • Breakdown by conditions • Narrow vs. Wide • High Ambient vs. Low Ambient • High Reflectivity vs. Low Reflectivity

11. Results – Display Quality

12. Results – Display Quality Target Tap Test • Best Condition: Wide, High Ambient, Low Reflective • Breakdown by conditions • Narrow vs. Wide • High Ambient vs. Low Ambient • High Reflectivity vs. Low Reflectivity

13. Results – Display Quality

14. Results – Tilt Angle

15. Results – Questionnaire • No two subjects agreed on an optimum tilt angle. • All subjects preferred Wide over Narrow and no Reflective cover (High vs. Low Reflectivity)

16. Results – Tilt Angle Rankings

17. Results – Questionnaire

18. Results - Questionnaire

19. Conclusions • Perceived comfort and usability is a combination of many factors, weighted differently for each candidate. A larger subject pool is necessary to make any definitive statement about which conditions are most important • Users always prefer a Wide filter and a Low Reflectivity surface. • In general, a 45 degree tilt angle +/- 15 degrees is preferred. • Based on the test data, 45 degrees is optimum for both reading and input tasks.

20. Questions?