Specular Reflection and Usability of
Tablet PCs
Specular Reflection and Usability of
Tablet PCsMy
eyes!
It burns!
Nooooo!Nooooo!
John GoreCOMP 7700Spring 2006
OutlineOutline
• Introduction• Specular Reflection• Experiment Design• Demonstration• Results• Conclusions
• Introduction• Specular Reflection• Experiment Design• Demonstration• Results• Conclusions
IntroductionIntroductionThe 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)
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)
Specular ReflectionSpecular ReflectionSpecular 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
Experiment – Conditions
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
• 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
Experiment – TestsExperiment – 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
• 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
Experiment – TestsExperiment – 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
• 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
Experiment – TestsExperiment – 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?”
• 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?”
Results – Display Quality
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
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
Results – Display Quality
Results – Display Quality
Display Quality - Reading Test
36.0
37.0
38.0
39.0
40.0
41.0
42.0
43.0
Narrow Wide High Amb Low Amb High Reflect Low Reflect
Condition
Avg sec/test
Results – Display Quality
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
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
Results – Display Quality
Results – Display Quality
Display Quality - Tap Test
1.06
1.07
1.08
1.09
1.10
1.11
1.12
1.13
Narrow Wide High Amb Low Amb High Reflect Low Reflect
Condition
Avg sec/target
Results – Tilt Angle
Results – Tilt Angle
Tilt Angle - Tap Test
1.10
1.15
1.20
1.25
1.30
1.35
0 30 45 60
Angle
Avg sec/target
Tilt Angle - Reading Test
34.0
36.0
38.0
40.0
42.0
44.0
46.0
48.0
0 30 45 60
Angle
Avg sec/test
Results – QuestionnaireResults –
Questionnaire• No two subjects agreed on an optimum tilt angle.
• All subjects preferred Wide over Narrow and no Reflective cover (High vs. Low Reflectivity)
• No two subjects agreed on an optimum tilt angle.
• All subjects preferred Wide over Narrow and no Reflective cover (High vs. Low Reflectivity)
Results – Tilt Angle Rankings
Results – Tilt Angle Rankings
Angle Acceptable
0 5
30 7
45 10
60 4
Angle Preferred
0 1
30 4
45 3
60 2
Results – QuestionnaireResults –
QuestionnaireDisplay Quality - Likert Scale
70.0
75.0
80.0
85.0
90.0
95.0
100.0
105.0
110.0
Narrow Wide High Amb Low Amb High Reflect Low Reflect
Condition
Points
Results - QuestionnaireResults -
QuestionnaireTilt Angle - Likert Scale
22.0
24.0
26.0
28.0
30.0
32.0
34.0
0 30 45 60
Condition
Points
ConclusionsConclusions• 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.
• 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.