1. A lifelog camera that processes a collection of still images for efficient transfer to an external memory, comprising: a camera module that captures still images according to an image capture routine of the lifelog camera; a memory in which the captured images are stored; and a control circuit configured to: generate a thumbnail image for each stored image, each thumbnail image stored in the memory at a resolution less than a resolution of the corresponding image; analyze the thumbnail images to identify one or more thumbnail images that meet transfer criteria for transfer of one or more of the captured images to the external memory, the external memory being remote from the lifelog camera, said analysis comprising i) determining which of the thumbnail images satisfy at least one transfer criterion, and ii) comparing only the thumbnail images that satisfy the at least one transfer criterion to determine a level of similarity between the thumbnail images that satisfy the at least one transfer criterion; and tag for transfer to the external memory the images that correspond to the thumbnail images that satisfy the at least one transfer criterion and meet a threshold level of similarity.