How Curiosity Gets a Close-Up on Mars to Come Out Sharp

Curiosity's Mars Hand Lens Imager — MAHLI — is a close-up camera mounted on the turret at the end of the rover's robotic arm. Getting a usable look at a nearby rock with it is not a matter of one lucky exposure. An onboard focusing process merges multiple images of the same target taken at different focus positions, creating a composite that brings as many features into focus as possible. The result is closer to a stack than a snapshot: sharpness comes from combining frames, and the merge is designed to hold as many features sharp at once as it can rather than betting everything on a single frame that happened to land in focus.