The portraits of James Barnor, Seydou Keïta and Malick Sidibé conjure up an image of cool modernity – but also draw on a long photographic tradition, writes Samuel Reilly

New-york , United-states , Monrovia , Montserrado , Liberia , Kinshasa , Democratic-republic-of-the-congo , Bight-of-benin , Ghana-general- , Ghana , Paris , France-general- ,