The present disclosure provides a description of various methods and systems associated with determining possible presence of Atrial Fibrillation (AF). In one example, a camera of a client device, such as a mobile phone, may acquire a series of images of a body part of a user. A plethysmographic waveform may be generated from the series of images. An autocorrelation function may be calculated from the waveform, and a number of features may be computed from the autocorrelation function. Based on an analysis of the features, a determination may be made about whether the user is experiencing AF. Such determined may be output to a display of the mobile phone for user review.