What looks to be a very interesting documentary on black photographers and photography will air tonight on PBS in the United States. Follow the link below for an interview with the filmmakers. I would guess that it will be available as Video On Demand and/or disc/download/etc. within a few months.

http://www.npr.org/blogs/codeswitch/2015/02/16/386011861/through-a-lens-darkly-black-photography-fades-up-to-joy