Free technical library

figure and background. Encyclopedia of visual illusions

At leisure / Visual (optical) illusions

 Comments on the article

<< Back: Changing terrain and perspective

>> Forward: portrait illusions

Let us point out here a number of visual illusions due to the influence of the contrast of brightness, i.e., the ratio of the difference between the brightness of the object and the background to the brightness of the background. We are used to always seeing objects and figures against one or another background. We have already pointed out (see paragraph 6) that when considering figures, we sometimes liken their parts to the figure as a whole. There it was a general psychological contrast.

What can be said about the brightness contrasts?

First, it turns out that on a darker background, we see the figures as lighter and, conversely, on a light background, as darker. This is evidenced by the figures shown in Fig. 101-103. By the way, the illusions due to the contrast of brightness shown in these figures can also be observed in the color performance of these figures.

Rice. 101. The shaded figure on the right seems lighter than the same figure on a light background on the left.

Rice. 102. The shaded figure on the right seems lighter than the same figure on a light background on the left.

Rice. 103. Crossroads of white stripes between black squares appear gray

Based on the above, the illusion of gray spots at the intersections of the black lines in Fig. 18 (see paragraph 3) can be partly explained by the phenomenon of irradiation, and partly by the influence of the brightness contrast. Finally, the illusions of Fig. 104-106 can no longer be explained only by the phenomenon of irradiation. For the first time they were compared and explained in the preface to his album of illusions by Ya. I. Perelman *.

* (Perelman Ya. I., Optical illusions, 1924.)

Rice. 104. Circles look like hexagons when viewed at close range.

Rice. 105. The same, but when viewed from a distance greater than in fig. 104

Rice. 106. Mugs also appear to be hexagons, although they are white and the background is black

Secondly, the phenomenon of the so-called edge contrast is interesting, which consists in the fact that it seems that the brightness of each rectangle of the figure in Fig. 107 are not the same, but somewhat darker at the borders with a lighter area and somewhat lighter at the borders with a darker one. Sometimes it even seems that these rectangles are shaded so as to give the impression of their transverse concavity. However, by obscuring adjacent stripes, one can be convinced that each individual strip has a completely uniform hatching.

Fig. 107

Thirdly, when perceiving the figure and the background, we tend to see, first of all, spots of a smaller area, as well as brighter, “protruding” spots, and most often the background seems to us to lie farther from us, behind the figure. The greater the brightness contrast, the better the object is visible and the more clearly its outline and shape are visible. We find examples of this in Fig. 108-111.

Rice. 108. First of all, we perceive either only the dark or only the light parts of the figure

Rice. 109. The letter C is seen more clearly (as more familiar) than the bright figure of the background surrounding the letter.

Rice. 110. First of all, most people see a vase in this picture, and then two silhouettes

Rice. 111. The same will happen when changing the brightness of the figure and background

To the reader who glances instantly at the horizontal top or middle row of black circles in Fig. 112, it is difficult to determine the number of circles placed to the left and right of the vertical bar. If these circles are arranged according to the so-called numerical figures, then it will not be difficult to count the circles at a glance.

Rice. 112. Circles arranged according to numerical figures can be counted instantly. And if the circles are in a line, can you just as quickly determine their number?

Finally, the phenomenon of "falling away to the background" of some parts of the figures is also interesting. So, if a rectangular object painted with black paint, as shown in Fig. 113, observed from some great distance on a white background, it will look approximately the same as shown in fig. 114. In this case, the white spots on the object, the thin lines of its contour and the sharp transitions from the figure to the background at the corners will disappear to the background, and the shape of the object will appear distorted. The eye very often takes a dark spot for a shadow from other nearby objects.

Fig. 113

Fig. 114

The visible shape and outline of objects can be distorted not only due to the falling off of parts of the contour to the background, but also due to such a spotty coloring of the object, when its contour seems deformed, distorted. For example, it is difficult to immediately say that in Fig. 115 shows the silhouette of a rabbit. Sometimes spotted coloration can take into account in advance the change in the brightness of local objects and the brightness of the background when they move, when the air mist flickers, when the sea surface is rough, when clouds move, etc.

Fig. 115

These principles are based on the camouflage coloring of objects with spots of different colors for the purpose of military camouflage. The same color "camouflage" is observed in the world of animals and plants, it serves as a protective color for them. There is an extensive specialized literature on the location of spots and the selection of masking colors for various objects.

The illusions presented in this section once again confirm the fact that their appearance largely depends on what kind of "interpretation" or "design" of the visible takes place in our minds.

Author: Artamonov I.D.

<< Back: Changing terrain and perspective

>> Forward: portrait illusions

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive information engine 12.11.2022 The highlight of the year was the development of the so-called information engine, fueled by information. The prototype engine did the job solely by calculation, without spending any energy on it. Unfortunately, this discovery works only in the microcosm. We all know about such a phenomenon as thermal noise. In the normal state, thermal fluctuations are random in nature and cannot do useful work. You can correct the situation with the help of feedback - information that could cut off the "braking" oscillations and fix the "working" ones. Then each time the engine would do only useful work, without spending energy on it in the form of fuel. The role of fuel in such a system would be played by information - this is a system for determining the perfect work and feedback that controls the engine. A group of physicists from Simon Fraser University in Burnab, British Columbia, and the Institute for Fundamental Questions (FQXi) conducted an experiment in which a bacterium-sized glass bead was moved in a given direction by means of thermal noise and information about its position. The bead was placed in water and caught in a laser trap. Thermal vibrations of water molecules pushed the bead in all possible directions, but thanks to measurements of its position in water and feedback, the optical trap only moved in space (and kept the bead at a new level) when the movement went in the right direction. The accuracy of determining the position of the bead in space left much to be desired, and thus the work of the "information" engine was small. It was possible to increase the efficiency of the engine after the inclusion in the algorithm of the so-called "Baesian solution estimation" - a statistical method that largely predicted the new position of the bead than measured it. In fact, the "fuel" of such an engine was only information about the approximate position of the bead obtained by measurement, a calculation algorithm that reduces the measurement error, and a feedback mechanism that fixes the bead (work performed) at a new level. The process of performing the work was carried out by thermal noise. You can say it's free. Now scientists are thinking about experiments on how to do similar work from other sources of noise. If everything works out, it will be possible to receive energy from sources that the world has not yet dreamed of.

Other interesting news:

▪ Most Power Efficient SRAM

▪ More solar panels in Tokyo

▪ Smallest black hole discovered

▪ Gadgets without batteries

▪ Songs in hours

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Signal limiters, compressors. Article selection

▪ article Histology. Crib

▪ article What does Grand Prix mean? Detailed answer

▪ article Art director of a club establishment. Job description

▪ article Universal electrician's probe. Encyclopedia of radio electronics and electrical engineering

▪ article Obedient ball. physical experiment

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024