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?”

DemonstrationDemonstration

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.

Questions?Questions?