Eigengrau

Self- gray, even its own light or noise floor ( the German name is also common in the English language ), is the color that you see in complete darkness. The term was introduced around 1860 by Gustav Theodor Fechner. At that time, noticed that at very large and very small magnitudes in the sensitivity of the eye is different from the prediction of Fechner 's law.

Self- gray is brighter perceived as black objects in low light conditions. The reason is that in the perception of contrast is more important than the actual brightness. For example, the night sky appears darker than intrinsically gray because of the star caused by the contrast. A pure black sensation of the eye is possible only with simultaneous contrast to a white sensation, as Ewald Hering in 1874 described.

The cause of the own gray action potentials of the optic nerve are considered to be caused by a kind of background noise of the retina, these random excitations can not be distinguished from those resulting from light particles. This is likely to thermally induced isomerization of the visual pigment rhodopsin. But there are also other hypotheses.

The lower sensitivity of the eye at low light intensity was reduced by Hermann von Helmholtz on the patchiness of its own horror.

The term self-noise is also used in other contexts, including in acoustics. An analogy to the self-noise is also found in photocells, especially when dark noise of the sensors of digital cameras.