According to Google this year
the rules included:
2 | Photographs
2.1 Must be the photographer’s own work
2.2 Must be portraits. ‘Portrait’ may be interpreted in its widest sense, of ‘photography concerned with portraying people with an emphasis on their identity as individuals’.
2.3 Must have been taken by the entrant from life and with a living sitter after 1 January 2015. Photographers must, if required, show proof of the date on which the photograph was taken.
2.4 Can be black and white or colour.
2.5 Must be unmounted and
on paper, or other suitable surface,
no larger than 1015 x 760mm and 20 kilos in weight (there are no limitations on how small a work can be). The image may be smaller than the paper size
2.6 All works must be submitted in either transparent protective sleeves (preferred) or similar transparent cover in order to protect during judging.
2.7 Photographers may submit individual portraits or portraits in series. A ‘series’ may mean either a group of separate portraits around a particular theme, or a number of pictures that when shown together combine to make up a single portrait work. The judges may choose to display a series in its entirety within the exhibition.