{"id":8857,"date":"2016-07-05T20:38:54","date_gmt":"2016-07-05T18:38:54","guid":{"rendered":"https:\/\/beta.optik-sport-shop.at\/?p=8857"},"modified":"2026-06-08T22:14:41","modified_gmt":"2026-06-08T20:14:41","slug":"light-in-the-eye","status":"publish","type":"post","link":"https:\/\/ddoptics.shop\/en\/licht-im-auge\/","title":{"rendered":"Function of the eye - adaptation to light and darkness"},"content":{"rendered":"
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The function of dark adaptation and light adaptation of light or on the retina in the eye<\/h2>\n

The retina of our eyes has two different types of sensory cells or receptors, on the one hand\u00a0the cones (for day vision)\u00a0<\/strong>and on the other hand\u00a0the rods (for night vision)<\/strong>.<\/p>\n

All photoreceptors are stimulated by the amount and spectrum of radiation. The cones are active in bright surroundings and automatically switch off in the dark. Although they are not very sensitive, unlike the rods they can\u00a0Recognise colours<\/strong>. There are\u00a0three types of cones<\/strong>. Each of the three cones has a different sensitive frequency range. A distinction is therefore made between\u00a0Sensors for blue, green-yellow and red<\/strong>.<\/p>\n

Seeing at night with binoculars<\/h3>\n

For night vision<\/strong>\u00a0are the sticks\u00a0<\/strong>(approx. 120 million). These are very sensitive to weak light stimuli (but cannot perceive colours and only react to differences in brightness and movement. The retina's sensitivity to light and dark is considerably increased. If you go outside at night from an illuminated room, the cones gradually switch off and the rods become active.<\/p>\n

Until the\u00a0rods have reached their highest possible sensitivity, it takes up to 45 minutes<\/strong>\u00a0- This adaptation period is also referred to as \"Dark adaptation<\/strong>\". Over the course of this period, sky observers recognise fainter and fainter stars. After just 15 minutes, the intensity of the dark adaptation has increased by a factor of 50,000. If you use white light at this point, you have to adapt again. After the start of the adaptation period, the\u00a0Retinal pit\u00a0<\/strong>no longer records images, it is switched off. In this state, the eye is colour-blind and sharp vision along the visual axis is no longer possible.<\/p>\n

This is also the reason,\u00a0why a misaligned telescope can no longer be focussed at night<\/strong>. This problem, which hunters have so far paid insufficient attention to, can be solved by focussing the binoculars on the expected main shooting distance while they are still bright and marking this setting. The eye only sees sharply in a very small area. This area is a small circle on the retina with a diameter of approx. 2 mm, which corresponds to a beam entrance angle through the pupil of only 2\u00b0. The visual fossa is located precisely in this area.<\/p>\n

The\u00a0Retinal pit is a depression in the retina,<\/strong>\u00a0where the point of sharpest vision is located in bright light.\u00a0The density of cones is highest in the retinal pit<\/strong>There are no rods in it. The density of the cones decreases towards the edge of the retina. These then mix with the\u00a0rods located further out on the retina<\/strong>.<\/p>\n

For this reason, objects can be seen most clearly during the day when looking directly at them, whereas at night you have to look a little past the object to see it clearly. For example, a sow changing colour at dusk is difficult or impossible to see with direct vision and only becomes visible with indirect vision (when the gaze wanders back and forth).\t\t<\/div>\n\t\t\t\t\t<\/div>\n\n\t<\/div>

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