Like most of Nikon's ultra-compact range the S640 is strictly a point-and-shoot camera, and has few manually adjustable settings. It does have a number of useful automatic features though, including lens-shift optical image stabilisation, allowing shake-free picture taking at shutter speeds as low as 1/15th of a second.
Main shooting modes include fully automatic, a selection of 17 scene mode programs, a Smart Portrait mode which includes face and smile detection, and Subject Tracking mode, useful for photographing moving subjects. It has Nikon's usual Best Shot Selector mode, which allows instant rejection of blurred shots, and the odd Multi-Shot 16 mode, which shoots an instant collage of 16 images arranged in a grid in one frame.
Unusually for a modern compact the video recording mode is a bit lacklustre, with a maximum resolution of 640 x 480 and 30fps, and with very poor quality mono audio via a noisy internal microphone. Needless to say the optical zoom cannot be used while recording.
The S640 has no spot metering, no tone, contrast or sharpness adjustment, and even the colour choices are limited to standard, vivid, monochrome, sepia or cyanotype. It does have 16 scene mode programs as well as automatic scene recognition. Other shooting options include a smart portrait mode with face detection, and a subject tracking AF mode for shooting moving subjects.