Four Thirds is a standard developed by Olympus and Panasonic for a 4/3rds-inch sensor format for digital photography. Four Thirds and Micro Four Thirds products include both digital cameras and video cameras. There are several companies developing products for the system in addition to Olympus and Panasonic, including Sigma, Tamron, Tokina, Samyang, Cosina (Voigtlander) and Carl Zeiss.