1. A method of selecting digital images from a first collection of digital images to specify a second collection of digital images, comprising: using a processor to store each digital image in the first collection of digital images at a storage location in an electronic storage and retrieval system; forming a corresponding machine-readable code for each stored digital image, the machine-readable code encoding an address reference to the address of the storage location of the corresponding digital image in the electronic storage and retrieval system; providing a viewable image that includes a representative image of each digital image in the first collection of digital images in association with its associated machine-readable code; and selecting one or more but not all of the digital images by: i) receiving address references or photographs of the machine-readable codes and extracting the address references from the received photographs; and ii) compiling the digital images corresponding to the received or extracted address references into the second image collection.