Comparison of Touch and Touchless Zoom Control Methods for Single-Handed Mobile Interaction

We conducted a user study comparing the accuracy and speed of three zoom methods for touch-screen devices. The comparison was between touch and touchless zoom methods. One method is GyroZoom which uses the mobile phone's rotation to zoom in and zoom out. It is named after the gyroscope sensor in smartphones to detect the angle and amount of device rotation. We constrained our research to single-handed interaction. The pinch-to-zoom method, also tested, is the standard touch-screen gesture method. VolumeZoom was the third method and does not require the user to touch the screen. Instead, the user presses the physical volume buttons that are normally used to increase or decrease volume; they were reprogrammed to perform zoom operations. The user study engaged 12 participants and employed a Google Pixel 3a smartphone. GyroZoom was 18.1% faster than the traditional pinch-to-zoom method and it was more efficient. VolumeZoom was the most efficient method of the three but was 18.9% slower than pinch-to-zoom. Participants gave favorable and preferential ratings for using GyroZoom and VolumeZoom over pinch-to-zoom in a single-handed usage scenarios.