Specular Reflection and Usability of Tablet PCs

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Specular Reflection and Usability of Tablet PCs
My eyes!

• Nooooo!

It burns!
John GoreCOMP 7700Spring 2006
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Outline

• Introduction
• Specular Reflection
• Experiment Design
• Demonstration
• Results
• Conclusions

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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)

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Specular Reflection

• Specular Reflection occurs when light bounces off
  a smooth surface into an observers eyes. For
  this to occur, the angle between the observers
  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

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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

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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

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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

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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?

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Demonstration
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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

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Results Display Quality
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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

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Results Display Quality
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Results Tilt Angle
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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)

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Results Tilt Angle Rankings
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Results Questionnaire
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Results - Questionnaire
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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.

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Questions?