Pioneer 11 was launched in April 1973 and flew through the Jovian system in December 1974. These are the best images of Callisto taken by Pioneer 11.
This image of Callisto only shows small color differences and small albedo variations, but a prominent light region is visible near the terminator. The image resolution is 391 km/pixel with a phase angle of 82 degrees. The image on the left is a color composite. The image on the right is the same image enhanced by computer processing.