Dating a photograph can be done in a number of ways. It’s possible to narrow down the date by ascertaining the technique used to produce the image. For example, if the work is an albumen print then it can’t have been made before 1850 and is less likely to have been made after 1905, when the popularity of the technique waned. If you use this method to date an image it’s useful to remember that older techniques were used by photographers long after they fall out of general fashion, and are used by contemporary photographers today. Another way to date a photograph containing people in it, is to date the clothing in the image. Taking a photograph was often a rarity and sitters often wore their best clothes and hairstyles. A good source for dating dress is the Victorian dress section of the Victoria & Albert Museum (click here for the website) or the multi-volume series of books ‘Fashion in Photographs’ (Batsford Fashion Guides, publ. 1991). For a list of books which can help further date your photographs please get in touch with the PCN. The National Portrait Gallery runs a free weekly opinion service, online and in person, with a member of curatorial staff to support research into British portraits; see here for details.