1. A face detection and recognition method, comprising: receiving a first preview image of a scene and a second preview image of nominally the same scene; determining whether the first preview image comprises one or more face regions; in response to determining that the first preview image comprises one or more face regions: determining a first location of a first face region in the first preview image; based at least in part on the first location of the first face region in the first preview image, predicting a second location in the second preview image of a second face region corresponding to the first face region in the first preview image; based at least in part on pixel information of the second face region in the second preview image, determining one or more characteristics of the second face region in the second preview image; based at least in part on the one or more characteristics of the second face region in the second preview image, determining one or more acquisition parameters for acquiring a main image of nominally the same scene; and acquiring the main image of nominally the same scene using the one or more acquisition parameters; wherein the method is performed using one or more computing devices.