Measuring 2D:4D finger length ratios with Smartphone cameras

Finger length ratios have received much attention among researchers as the 2D:4D ratio has been linked to several physical and mental characteristics. This study explores the feasibility of using a Smartphone as an instrument for measuring finger length ratios. The approach taken in this study is to use the Smartphone camera to take freehand photos of the hand which is subsequently subjected to image analysis. Measurement procedures include hand near and far from the body, palms up or down, or hands in mid air versus hands resting on a flat surface. Experimental evaluations show that the most accurate measurements are achieved by resting the hand on a surface with the palm facing up. These results are comparable to those achieved with conventional procedures with an error of 1%.