Previous research has not adequately investigated important parameters, namely range of operation and preference, for zooming and rotation using pinch gestures. This study obtained these parameters on 23-inches multi-touch screens at vertical (75°) and horizontal (15°) inclinations. Forty right-handed participants with an age range of 22 to 32 years old (24.48 ± 2.52 years old) were recruited to perform experimental tasks. Rotation tasks were performed using two different finger strategies (fixed thumb and moving both fingers/float). The data showed that the maximal and comfortable pinch in zooming were around 570 and 386 in pixels (155 and 105 in millimeters) for both hands while the range of rotation (RoR) were 83-degrees clockwise and 119-degrees counterclockwise using the dominant hand from the preferred angle of orientation (PAO). A value of approximately 68% of the maximal pinch distance was the comfortable pinch distance. This study also found that participants preferred around 29-degree clockwise PAO for the right hand and 33-degree counterclockwise PAO for the left hand to initiate rotation. Rotating with fixed thumb significantly reduced the range of rotation. The vertical inclination allowed users to have longer pinch distance, wider RoR, and was subjectively preferred. These findings could be used for guidelines in multi-touch pinch manipulation using virtual rotary knobs.

Previous research has not adequately investigated important parameters, namely range of operation and preference, for zooming and rotation using pinch gestures. This study obtained these parameters on 23-inches multi-touch screens at vertical (75°) and horizontal (15°) inclinations. Forty right-handed participants with an age range of 22 to 32 years old (24.48 ± 2.52 years old) were recruited to perform experimental tasks. Rotation tasks were performed using two different finger strategies (fixed thumb and moving both fingers/float). The data showed that the maximal and comfortable pinch in zooming were around 570 and 386 in pixels (155 and 105 in millimeters) for both hands while the range of rotation (RoR) were 83-degrees clockwise and 119-degrees counterclockwise using the dominant hand from the preferred angle of orientation (PAO). A value of approximately 68% of the maximal pinch distance was the comfortable pinch distance. This study also found that participants preferred around 29-degree clockwise PAO for the right hand and 33-degree counterclockwise PAO for the left hand to initiate rotation. Rotating with fixed thumb significantly reduced the range of rotation. The vertical inclination allowed users to have longer pinch distance, wider RoR, and was subjectively preferred. These findings could be used for guidelines in multi-touch pinch manipulation using virtual rotary knobs.

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