What is the standard SI unit for luminous intensity?

The story behind the answer

Candela is the SI base unit for luminous intensity—the perceived power of light in a specific direction. It’s defined so that a source emitting monochromatic light at 540 THz (green) with a radiant intensity of 1/683 watt per steradian has an intensity of 1 candela. By contrast, the lumen measures total light output (luminous flux) and equals candela × steradian.

Remember it this way: “candle → candela” for how bright a source appears in a given direction. The other options are not units of luminous intensity: lumen is flux, coulomb measures electric charge, and the faraday relates to electrochemistry (e.g., the Faraday constant). Candela’s status as a base SI unit highlights how central human visual response is in photometry.