Day-for-night is a film-maker's term for simulating night by shooting during the day with appropriate filters. Technology is busy making that obsolete with cameras that see brightness and color at night with no help and which don't have that black-and-white infrared or green nightvision look. None, however, can match Sony's newest.
The A7s is one of a trio of full-frame (same area as a still, 35mm film frame) mirrorless (i.e., non-DSLR) cameras, a category dominated by Sony because no one else makes full-frame mirrorless cameras. The A7s is "only" a 12-megapixel camera, which means that the sensils (sensor pixels) are bigger, and therefore catch more photons, than those in lessor digital cameras, which means they should perform better in low light. Boy do they.
How much better? Watch the video below and you'll see highlights clipping (overexposure) when the full moon comes into view. Wild, crazy and about $2500 from reputable U.S. dealers. More if you want a lens, although both Canon and Nikon lenses can be fitted to the camera with an adapter.
It shoots 4k video too, but not internally — only to an expensive ($2,000) external recorder. Phillip Bloom reviewed the A7s here and was as wowed by the low light prowess of the thing as everyone else, but was not amused by the severe jello effect (rolling shutter) that the camera exhibits when panning quickly.