Eigengrau
Also called: Brain grey · Intrinsic grey · Dark light
The colour you see in total darkness is not black. It is a very dark grey, most likely because the light-sensing cells in your eyes fire a little even when no light reaches them.
How common
Does this happen to you?
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.
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 most likely the grey. Other noise in the retina cannot be fully ruled out1.
Contrast 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
- Go into a room you can make fully dark. A bathroom with the door closed at night works.
- Wait at least 10 minutes. Your eyes take 20 to 30 minutes to adapt fully to the dark5.
- Look straight ahead with your eyes open. Notice that the field is grey, not black.
- 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.
Is it a problem?
No. Seeing dark grey instead of pure black in the dark is normal1. It is not a sign of an eye problem. Faint moving speckle or colour on top of the grey is also usually harmless, covered under closed-eye hallucinations3.
See a doctor if you notice:
- new flashes of light,
- a shower of floaters,
- a shadow across part of your vision.
Those can signal a retina problem, unlike eigengrau.
History and culture
The older name Eigenlicht, which means “intrinsic light”, dates back to the 19th century1.
Sources and further material
Missing something your body does? Tell me about it.
Related oddities
Closed-eye hallucinations
Close your eyes and you do not see nothing. You see speckle, drifting colour, and, as you fall asleep, moving patterns and even scenes. Almost everyone sees the speckle, and many people see more. Almost nobody talks about them.
Visual snow
Tiny flickering dots across the whole field of vision, like static on an old TV, present with eyes open or closed. About 2% of people have it. The eyes are fine. The visual part of the brain is over-active.
Phosphenes
The flashes, rings, and patterns of light you see when you rub or press your closed eyes, or after a knock on the head. Pressure on the eye makes the retina fire without any light.
Prisoner's cinema
After hours or days in darkness, people start to see light shows: colours, geometric patterns, and sometimes figures or scenes. Prisoners, truck drivers, pilots, and meditators all report it.