Dark adaptation time of a normal eye. Vision adaptation

When moving from bright light to complete darkness(so-called dark adaptation) and during the transition from darkness to light (light adaptation). If an eye that was previously exposed to bright light is placed in the dark, its sensitivity increases at first quickly, and then more slowly.

The process of dark adaptation takes several hours, and by the end of the first hour the sensitivity of the eye increases several times, so that the visual analyzer is able to distinguish changes in the brightness of a very weak light source caused by statistical fluctuations in the number of emitted photons.

Light adaptation occurs much faster and takes 1-3 minutes at average brightness. Such large changes in sensitivity are observed only in the eyes of humans and those animals whose retina, like that of humans, contains rods. Dark adaptation is also characteristic of cones: it ends faster and the sensitivity of cones increases only 10-100 times.

Dark and light adaptation of the eyes of animals have been studied by studying the electrical potentials arising in the retina (electroretinogram) and in the optic nerve under the influence of light. The results obtained are generally consistent with data obtained for humans using the adaptometry method, based on a study of the appearance of the subjective sensation of light over time after a sharp transition from bright light to complete darkness.

Links

Lavrus V.S. Chapter 1. Light. Light, vision and color // Light and heat. - International public organization“Science and Technology”, October 1997. - P. 8.

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See what “Eye Adaptation” is in other dictionaries:

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Adaptation of the eye to changing lighting conditions. When moving from bright light to darkness, the sensitivity of the eye increases, and when moving from darkness to light it decreases. The spectrum is also changing. sensitivity of the eye: perception of the observed... ... Natural science. Encyclopedic Dictionary

- [lat. adaptatio adjustment, adjustment] 1) adaptation of the body to environmental conditions; 2) processing of the text in order to simplify it (for example, an artistic prose work in foreign language for those who are not good enough... ... Dictionary foreign words Russian language

Not to be confused with Adaptation. Adaptation (lat. adapto I adapt) the process of adapting to changing conditions external environment. Adaptive system Adaptation (biology) Adaptation (control theory) Adaptation in processing... ... Wikipedia

Adaptation- introduction of changes to the IR EGKO of Moscow, carried out exclusively for the purpose of their functioning on specific technical means user or under the control of specific user programs, without consent these changes With… … Dictionary-reference book of terms of normative and technical documentation

sensory adaptation- (from Latin sensus feeling, sensation) an adaptive change in sensitivity to the intensity of the stimulus acting on the sense organ; can also manifest itself in a variety of subjective effects (see consistent about ... Great psychological encyclopedia

DARK ADAPTATION, slow change in sensitivity human EYE at the moment when a person enters an unlit space from a brightly lit space. The change occurs due to the fact that in the RETINA of the eye, with a decrease in total... ...

ADAPTATION- (from lat. adaptare), adaptation of living beings to environmental conditions. A. the process is passive and comes down to the body’s reaction to physical changes. or physical chem. environmental conditions. Examples A. In freshwater protozoa, osmotic. concentration... ... Big medical encyclopedia

- (Adaptation) ability retina eyes adapt to a given intensity of illumination (brightness). Samoilov K.I. Marine dictionary. M.L.: State Naval Publishing House of the NKVMF of the USSR, 1941 Adaptation of the body's adaptability ... Marine Dictionary

ADAPTATION TO LIGHT, shift in functional dominance from rods to cones (visual cells different types) in the RETINA with increasing lighting brightness. Unlike ADAPTATION to DARKNESS, light adaptation occurs quickly, but creates... ... Scientific and technical encyclopedic dictionary

Books

The Painted Veil: Intermediate Reading Book, Maugham William Somerset. The title of the novel The Patterned Veil, written in 1925 by the British classic William Somerset Maugham, reflects the lines of Percy Bysshe Shelley’s sonnet Lift not the painted veil which...

It is known that the human eye is capable of working at very wide range brightness. However, the eye cannot perceive this entire range at the same time. During vision, the eye adapts to the prevailing brightness level in the visual field. This phenomenon is explained by the dependence of the light sensitivity of the eye on the level of its excitation photosensitive elements. The eye has maximum light sensitivity after a long stay in the dark. In light, the sensitivity of the eye decreases. Adaptation process visual organ a person to different levels of brightness is usually called brightness adaptation.

It has been experimentally shown that the range of perceived brightness at a given level of adaptation is very limited. All surfaces that have a brightness less than the minimum for a given range appear black to us. Maximum brightness creates the feeling of white. If a surface appears in the field of view, the brightness of which exceeds the maximum for a given range, then the adaptation of vision will change, and the entire range of vision will correspondingly shift towards higher brightnesses. At the same time, those surfaces that seemed gray to us at a lower level of adaptation will be perceived as black.

Brightness adaptation occurs as a result of changes in the brightness of the visual field, and, consequently, the illumination of the retina in the image area. Special cases of brightness adaptation are dark And light adaptation. Dark adaptation occurs when the brightness of the visual field instantly decreases from a certain value to zero adaptation brightness value. Light - when brightness increases from its zero value to a certain finite value. The duration of the processes of light and dark adaptation is different. While a decrease in visual sensitivity (light adaptation) occurs in a time from a fraction of a second to several seconds, the process of dark adaptation lasts 60...80 minutes.

If you observe a sheet of white paper for 10...15 seconds, half of which is covered with something black, and then remove the black, then the previously covered part of the sheet will seem lighter than the rest of it. In this case, it is customary to talk about local brightness adaptation. The phenomenon of local brightness adaptation can be explained by the fact that when details of different brightness are simultaneously observed, i.e., when the illumination of different areas of the retina at the same time is different, the level of excitation of some areas affects the light sensitivity of others.

Color adaptation occurs as a result of a change in the color of the visual field while its brightness remains unchanged. While luminance adaptation is characterized by a discrepancy between lightness and brightness, color adaptation is characterized by a discrepancy between the chromaticity of the radiation and the sensation of this chromaticity.

The phenomenon of color adaptation is explained by a change in the sensitivity of the eye as a result of a change in the ratio of the excitation levels of its three receivers when the eye is exposed to radiation of a certain color. Color, on

which the eye adapts, fades, as it were. This occurs as a result of a decrease in the sensitivity to a given color of the part of the retina that is adapted to this color. So, if, after observing a green figure for 15...20 seconds, you turn your gaze to an achromatic background, then a consistent image (a trace from the previous irritation) of a reddish color appears on the background. If you look through yellow glasses for some time, then after the glasses are removed, all surrounding objects will appear bluish. The change in color as a result of the preliminary action of other colors on the eye is called consistent color contrast. It has been experimentally shown that changes in the sensation of color during the process of color adaptation can be quite large, and the nature of the change in color does not depend on the brightness of the observed color.

Depending on the presence of details of different colors in the field of view, changes in visual contrasts may occur due to both changes in lightness and changes in chromaticity. Details covered in dark background, they lighten, but on light they darken. Thus, two pieces of the same paper, placed in one case on black velvet, and in the other on white fabric, seem unequal in lightness. The lightness of a detail changes under the influence of the background color, regardless of whether the background and the detail viewed on it are achromatic or colored.

Having placed pieces of the same gray paper on backgrounds of different colors, we will notice that these pieces will seem to us different in color tone. On a red background, a gray field will take on a greenish tint, on a blue background it will become yellowish, and on a green background it will become reddish. Similar phenomenon is also observed if pieces of paper of colors different from the background color are placed on colored backgrounds: yellow on red will seem slightly greenish, yellow on green - orange, etc. This phenomenon, in contrast to consistent contrast, is called simultaneous color contrast.

It is known that the same sheet of white paper is perceived as “white” in any lighting conditions: by candlelight, incandescent lamps and daylight. Despite the fact that differences in the spectral composition of “white” light sometimes exceed differences in the spectral reflectance curves of most objects, the eye almost always accurately determines the colors of objects. So, for example, although surfaces that are blue in daylight conditions turn out to be greenish when illuminated by incandescent lamps, a person continues to consider them blue. This is explained by the fact that in any lighting conditions, white details are most easily recognized, since they are always the lightest. All other colors are evaluated by the eye in relation to them. In other words, when observing a certain scene containing a number of colored objects, under certain lighting conditions, the relative sensitivities of the three eye receivers change in such a way that the ratio of their excitation levels in the part of the retina where the image of the lightest object in the scene appears becomes equal to the ratio of excitation levels sensational white. This phenomenon is called the phenomenon color constancy, or lighting corrections. This phenomenon explains, for example, that the viewer, when watching films (in a darkened room), does not notice

Light perception is an ability visual analyzer perceive light and distinguish between degrees of brightness. When studying light perception, the ability to distinguish between minimal light irritation - the irritation threshold - and to capture the smallest difference in the intensity of illumination - the threshold of discrimination.

The process of adaptation of the eye to different conditions lighting is called adaptation. There are two types of adaptation: adaptation to darkness when the light level decreases and adaptation to light when the light level increases.

Everyone knows how helpless you feel when you go from a brightly lit room to a dark one. Only after 8-10 minutes does the discrimination of poorly lit objects begin, and in order to navigate sufficiently freely, it takes at least another 20 minutes until visual sensitivity in the dark reaches the degree necessary for this. With dark adaptation, sensitivity to light increases, maximum adaptation is observed after an hour.

Reverse process of adaptation to high level illumination proceeds much faster than adaptation to darkness. When adapting to light, the sensitivity of the eye to the light stimulus decreases; it lasts about 1 minute. Upon leaving a dark room, visual discomfort disappears after 3-5 minutes. In the first case, during the process of dark adaptation, scotopic vision appears, in the second, during light adaptation, photopic vision appears.

The visual system responds adequately to both fast and slow changes in radiant energy. Moreover, it is characterized by an almost instantaneous reaction to a rapidly changing situation. The light sensitivity of the visual analyzer is as variable as the characteristics of light stimuli in the world around us are varied. The need to adequately perceive the energy of both very weak and very strong light sources, without undergoing structural damage, is ensured by the ability to rearrange the operating mode of the receptors. In the bright light light sensitivity eyesight decreases, but at the same time the reaction to spatial and temporal differentiation of objects intensifies. In the dark, the whole process happens in reverse. This set of changes in both photosensitivity and resolution of the eye depending on external (background) illumination is called visual adaptation.

The scotopically adapted retina is maximally sensitive to the light energy of the low level, but at the same time its spatial resolution sharply decreases and color perception disappears. The photopicly adapted retina, being low-sensitive for distinguishing weak light sources, at the same time has high spatial and temporal resolution, as well as color perception. For these reasons, even on a cloudless day, the moon fades and the stars go out, and at night, without backlighting, we lose the ability to read text, even in large print.

The range of illumination within which visual adaptation occurs is enormous; in quantitative terms it is measured from a billion to several units.

Receptors in the retina have very high sensitivity- they can be irritated by one quantum of visible light. This is due to the action of the biological law of amplification, when after the activation of one rhodopsin molecule, hundreds of its molecules are activated. In addition, the retinal rods are organized into large functional units in low light. Impulse from large quantity rods converge into bipolar and then into ganglion cells, causing an amplification effect.

As the illumination of the retina increases, vision, determined mainly by the rod apparatus, is replaced by cone vision, and the maximum sensitivity shifts in the direction from the short-wavelength to the long-wavelength part of the spectrum. This phenomenon, described by Purkinje back in the 19th century, is well illustrated by everyday observations. In a bouquet of wildflowers, yellow and red poppies stand out on a sunny day, and blue cornflowers at dusk (the maximum sensitivity shift is from 555 to 519 nm).

To distinguish colors crucial has their brightness. The eye's adjustment to different brightness levels is called adaptation. There are light and dark adaptations.

Light adaptation means a decrease in the eye's sensitivity to light in high light conditions. During light adaptation, the cone apparatus of the retina functions. Practically, light adaptation occurs in 1–4 minutes. The total light adaptation time is 20-30 minutes.

Dark adaptation- This is an increase in the sensitivity of the eye to light in low light conditions. During dark adaptation, the rod apparatus of the retina functions.

At brightnesses from 10-3 to 1 cd/m2, collaboration rods and cones. This is the so called twilight vision.

Color adaptation involves a change in color characteristics under the influence of chromatic adaptation. This term refers to a decrease in the eye's sensitivity to color when observing it for a more or less long time.

4.3. Patterns of color induction

Color induction is a change in the characteristics of a color under the influence of observing another color, or, more simply, the mutual influence of colors. Color induction is the desire of the eye for unity and integrity, for the closure of the color circle, which in turn serves as a sure sign of a person’s desire to merge with the world in all its integrity.

At negative Induction, the characteristics of two mutually inducing colors change in the opposite direction.

At positive Induction, the characteristics of colors come closer together, they are “trimmed” and leveled.

Simultaneous induction is observed in any color composition when comparing different color spots.

Consistent induction can be observed in a simple experiment. If you place a colored square (20x20 mm) on white background and fix your gaze on it for half a minute, then on a white background we will see a color contrasting with the color of the paint (square).

Chromatic induction is a change in the color of any spot on a chromatic background in comparison with the color of the same spot on a white background.

Luminance induction. With a large contrast in brightness, the phenomenon of chromatic induction is significantly weakened. The smaller the difference in brightness between two colors, the more the perception of these colors is affected by their hue.

Basic patterns of negative color induction.

The degree of induction staining is influenced by the following: factors.

Distance between spots. The smaller the distance between the spots, the greater the contrast. This explains the phenomenon of edge contrast - an apparent change in color towards the edge of the spot.

Contour clarity. A sharp outline increases luminance contrast and reduces chromatic contrast.

The ratio of brightness of color spots. The closer the brightness values of the spots, the stronger the chromatic induction. Conversely, an increase in luminance contrast leads to a decrease in chromatic contrast.

Spot area ratio. The larger the area of one spot relative to the area of the other, the stronger its inductive effect.

Saturation of the spot. The saturation of a spot is proportional to its inductive effect.

Observation time. When the spots are fixed for a long time, the contrast decreases and may even disappear completely. Induction is best perceived with a quick glance.

The area of the retina that detects color spots. The peripheral areas of the retina are more sensitive to induction than the central one. Therefore, color relationships are more accurately assessed if you look slightly away from the place of their contact.

In practice, the problem often arises weakening or eliminating induction staining. This can be achieved in the following ways:

by mixing the background color into the spot color;

outlining the spot with a clear dark outline;

generalizing the silhouette of spots, reducing their perimeter;

mutual removal of stains in space.

Negative induction can be caused by the following reasons:

local adaptation– a decrease in the sensitivity of the retinal area to the fixed color, as a result of which the color that is observed after the first one seems to lose the ability to intensely excite the corresponding center;

autoinduction, i.e., the ability of the organ of vision, in response to irritation by any color, to produce the opposite color.

Color induction is the cause of many phenomena united by the general term “contrasts”. In scientific terminology, contrast generally means any difference, but at the same time the concept of measure is introduced. Contrast and induction are not the same thing, since contrast is a measure of induction.

Luminance Contrast characterized by the ratio of the difference in brightness of spots to greater brightness. Brightness contrast can be high, medium or low.

Contrast by saturation characterized by the ratio of the difference in saturation values to greater saturation . The contrast in paint saturation can be large, medium or small.

Contrast in color tone characterized by the size of the interval between colors in a 10-step circle. The contrast in color tone can be large, medium or small.

Big contrast:

high contrast in color tone with medium and high contrast in saturation and brightness;

medium contrast in hue with high contrast in saturation or brightness.

Medium Contrast:

average contrast in hue with average contrast in saturation or brightness;

low contrast in hue with high contrast in saturation or brightness.

Small contrast:

low contrast in color tone with medium and low contrast in saturation or brightness;

medium contrast in hue with low contrast in saturation or brightness;

high contrast in color tone with low contrast in saturation and brightness.

Polar contrast (diametrical) is formed when differences reach their extreme manifestations. Our senses function only through comparisons.

The peripheral organ of vision reacts to changes in lighting and functions regardless of the degree of brightness of the lighting. Adaptation of the eye is the ability to adapt to different levels illumination The reaction of the pupil to the changes that occur gives the perception of visual information in the millionth intensity range from lunar to bright lighting, despite the relative dynamic response volume of visual neurons.

Types of adaptation

Scientists have studied the following types:

light - vision adaptation in daylight or bright light;
dark - in darkness or low light;
color - conditions for changing the color of the illumination of objects located around.

How does it happen?

Light adaptation

Occurs during the transition from darkness to strong light. It instantly blinds and initially only white is visible, since the sensitivity of the receptors is tuned to dim light. It takes one minute for the cones to hit the sharp light to capture it. With addiction, the retina's light sensitivity is lost. Complete adaptation of the eye to natural light occurs within 20 minutes. There are two ways:

a sharp decrease in retinal sensitivity;
reticular neurons undergo rapid adaptation, inhibiting rod function and favoring the cone system.

Dark adaptation

The dark process occurs during the transition from a brightly lit area to a dark one.

Dark adaptation is the reverse process of light adaptation. This happens when moving from a well-lit area to a dark area. Initially, blackness is observed as the cones cease to function in low intensity light. The adaptation mechanism can be divided into four factors:

Light Intensity and Timing: By increasing pre-adapted brightness levels, the cone mechanism's dominance time is extended while the rod mechanism's switching is delayed.
Retinal size and location: The location of the test spot influences the dark curve due to the distribution of rods and cones in the retina.
The wavelength of threshold light directly affects dark adaptation.
Rhodopsin regeneration: when exposed to light photopigments, structural changes occur in both rod and conical photoreceptor cells.

It is worth noting that night vision has much more low quality than vision in normal light, as it is limited by reduced resolution and provides the ability to distinguish only shades of white and black. It takes about half an hour for the eye to adapt to twilight and acquire sensitivity hundreds of thousands of times more than in daylight.

It takes much longer for older people to adjust their eyes to the dark than for younger people.

Color adaptation

For humans, color objects change under different lighting conditions only for a short period of time.

It consists of a change in the perception of the retinal receptors, in which the maxima of spectral sensitivity are located in different color spectrums radiation. For example, when changing natural daylight to indoor lamp light, changes will occur in the colors of objects: green will be reflected in a yellow-green tint, pink - red. Such changes are visible only for a short period of time; over time they disappear and the color of the object appears to remain the same. The eye gets used to the radiation reflected from the object and is perceived as in daylight.