An apparatus has two optical portions, for capturing imagery from two directions. One portion captures imagery from the user (e.g., the user's retina), and the other captures imagery from another subject. In one arrangement, each optical portion has its own image sensor, and the two portions operate at the same time to capture imagery. Information derived from the imagery of the user (e.g., a hash) can be used—in consultation with a database—to attempt to identify the user. Such an image hash can be steganographically embedded into the subject-related image information. A great number of other features and arrangements are also detailed.