A single-pixel camera resembles an artist painting through a stencil with many holes. Each frame lets in only part of the light, and then the computer assembles a whole image from this mosaic. Previously, the mask sequence was fixed, as if the artist always used the same stencil, never squinting at the scene. The new method lets the camera choose the mask order itself: it kind of squints to first capture the main outlines, then focuses on fine details where they really exist. This way, the device can even distinguish shades invisible to the eye in the infrared 'thermal' range.

Paradoxically, a single sensor can spot traces of chemicals on an apple, even though it looks perfect on the outside.