- The photograph is an object independent of its content with characteristics such as size, shape, and (probable) technique for production. It will also have a provenance trail that can be investigated independently (where did you get it; what was it stored with; who owned it first?).
- The image will also have an author (creator), whether that is a professional photographic studio or an amateur snapshooter. Each of these will impart time-related characteristics that can be investigated.
- Finally the content of the image will be a rich source of evidence, both in its focus area (usually people) and its field (the background). By the presence or absence of particular technologies (power lines, paved street, car models, advertisements) the field can indicate both time and place. The individuals pictured will display characteristics (fashions) that varied with time: such as clothing, hairstyles, whiskers, hats, furniture or jewelry.
Once a probable time period has been identified, this can be linked to other forms of genealogical evidence to determine just who is shown in the picture.
Helen recommended the following titles for further reading on relevant techniques or as essential references for dating. (Hyperlinks are to Trove Books, where you check the availability of each title in libraries.)
- The mechanical eye in Australia : photography 1841-1900 / Alan Davies & Peter Stanbury
- Australians behind the camera : directory of early Australian photographers, 1841 to 1945 / Sandy Barrie
- Tracing your ancestors through family photographs : a complete guide for family and local historians / Jayne Shrimpton
- Family photographs & how to date them / Jayne Shrimpton
- The dead horse investigation : forensic photo analysis for everyone / Colleen Fitzpatrick
- Dating old photographs / Robert Pols
- Ashford in old photographs / collected by Richard Filmer.
- Victorian photographers at work / John Hannavy