jäännöskuvan

Jäännöskuvan, often translated as afterimage, is a visual phenomenon that occurs when a person stares at a bright or intense object for a period of time and then looks away. A faint, reversed image of the original object, often in complementary colors, can be perceived in the same location. This is primarily due to the properties of photoreceptor cells in the retina, specifically the rods and cones.

When exposed to intense light, these photoreceptors undergo a process called photochemical bleaching. This means that the light-sensitive pigments within them are temporarily depleted. After the stimulus is removed, these pigments need time to regenerate. During this regeneration period, the photoreceptors become less sensitive to light.

When the viewer then looks at a uniform surface, the areas of the retina that were stimulated by the original object will be less responsive than the surrounding areas. This difference in responsiveness is interpreted by the brain as an image. The color of the afterimage is complementary because the cone cells responsible for detecting specific colors become fatigued. For example, staring at a red object will cause the red-sensitive cones to become less responsive, leading to the perception of a green afterimage when looking at a white surface.

There are two main types of afterimages: positive and negative. Positive afterimages are similar in color to the original stimulus and are brief, lasting only a fraction of a second. Negative afterimages are complementary in color and are more persistent, lasting for seconds or even minutes. The duration and intensity of an afterimage depend on factors such as the brightness and duration of the original stimulus, as well as individual physiological differences.