Duration of Copyright depends on when a photograph was taken because provisions of all the Acts of 1862, 1911, 1956 and 1988 were carried over by the succeeding Act even if the old Act was repealed. It’s not enough to say that copyright in most photographs is 70 years pma because of the complications of the earlier Acts.
Photographs taken before 1 July 1912 - the day the 1911 Copyright Act became law
These are out of copyright but this does not mean a free for all because the owner of the physical photograph has rights and will need to agree to publication.
see Publication Right
Photographs taken between 1 July 1912 and 31 May 1957 - the day before the 1956 Copyright Act became law
Copyright will expire fifty years from the end of the year in which the photograph was taken or seventy years after the death of the photographer, whichever is the longer.
Photographs taken between 1 June 1957 and 31 July 1989 - the day before the 1988 Copyright Act became law
Copyright expires fifty years after the end of the year in which the photograph was published or seventy years after the death of the photographer, whichever is the longer. If the photograph remained unpublished on 31 July 1989, copyright will expire on 31 December 2039 (fifty years after the implementation of the 1988 Act) or seventy years after the death of the photographer, whichever is the longer.
Photographs taken after 1 August 1989 - the day the 1988 Copyright act became law
Copyright expires seventy years after the death of the photographer, whether published or not.
Photographs taken by unknown photographers
Any photograph taken by an unknown photographer at any date before 1 August 1989 is protected for seventy years from the end of the year in which the photograph was taken - always assuming a year can be deduced - or the end of 2039, whichever is the later. This applies whether the photograph has been published or not. Photographs taken by unknown photographers after 1 August 1989 have the same protection although discovering when the photographer dies may not be easy if his identity is unknown.
Any unknown photograph which is clearly later than 1 July 1912 should be treated with caution. It is not unknown for a photographer to creep out of the woodwork when an early work is published. Bear in mind that a photograph taken by a young photographer in 1935 was out of copyright at the end of 1985 but in 1996, this copyright was revived. He may now be an old man but nevertheless, his copyright remains with him and his heirs for seventy years pma. A photograph taken by a fifteen year old in 1915 will have expired in 1965, been revived in 1996 and assuming the photographer lived to be ninety-five, will not now expire until 2065. This is all dependent upon whether the photographer was commissioned or employed in which case, it could be the commissioner or the employer who prepares to do battle but it is foolhardy to assume that because a photograph is old, it is out of copyright.
However, see Orphan Works which has considerably muddied the waters.