1. A camera comprising: a first image generating unit for generating a first image that contains a subject image and an autofocus marker superimposed on the subject image; a buffer memory for storing the first image; a second image generating unit for generating a second image by erasing the autofocus marker from the first image stored in the buffer memory; a face detection unit for performing face detection using the second image; and a tracking unit for tracking a subject using the output of the face detection unit.