From WikiGTA - The Complete Grand Theft Auto Walkthrough
|GTA Vice City
GTA San Andreas
Liberty City Stories
The camera is available in GTA Vice City for the first time, although it is only possible in GTA San Andreas to view your pictures. The camera in GTA Vice City is only used in the mission Martha's Mug Shot, to make pictures of Alex Shrubs affair with Candy Suxxx.
In GTA San Andreas, your pictures are saved in a gallery, and on the PC-version they even appear as screenshot in your userfiles (My documents\GTA San Andreas userfiles\Gallery). The camera is also needed to make the snapshots in San Fierro.
Screenshots you make with the camera in GTA Vice City, GTA Liberty City Stories and GTA Vice City Stories are not saved.