Eigengrau

How it works

Close your eyes in a fully dark room. What you see is not black. It is a uniform dark grey. The German word for it is Eigengrau, which means “own grey”¹. It is often approximated on screens by the colour #16161D¹.

The grey comes from the rod cells in your retina. A rod contains a pigment called rhodopsin. When light hits rhodopsin, the molecule changes shape and the rod sends a signal². The molecule can also change shape on its own, by pure heat, with no light involved. This happens about once every 100 seconds in each rod¹. A single event is rare for one molecule, but each eye has about 92 million rods⁴, so the retina produces a steady trickle of false signals in the dark.

The brain cannot tell a heat-triggered signal from a light-triggered one. It reads the trickle as faint light. That is the grey¹.

The same noise also explains why a black object in daylight looks darker than eigengrau. In daylight, contrast with the bright surroundings pushes the black below the baseline. In full darkness there is no contrast, so you only see the baseline¹.

Eigengrau is rarely flat. Most people see faint moving speckle and slow blobs of colour on top of it. Those are covered under closed-eye hallucinations³.

Try it

1. Go into a room you can make fully dark. A bathroom with the door closed at night works.
2. Wait 2 or 3 minutes so your eyes adapt.
3. Look straight ahead with your eyes open. Notice that the field is grey, not black.
4. Now hold a black object, such as a phone with the screen off, in front of a dim light. Compare. The object looks darker than the dark did.

History and culture

The word comes from 19th-century German research on vision¹. The idea that darkness has a colour surprised people then, and it still does.