Some HP, Dell, Lexmark and Canon printers can operate with a 'photo' cartridge. These cartridges will fit into the BLACK port, and work alongside the usual colour cartridge. They are designed to offer the very best colour definition possible when you are printing photographs – by giving the printer a total palette of six colours.
If you print mainly black and colour documents then using a photo cartridge isn’t beneficial. Photo cartridges contain a very small amount of black ink (about one-third of the black-only cartridge).