Vision and art the biology of seeing pdf

Date published 


download Vision and Art: The Biology of Seeing on ✓ FREE SHIPPING on qualified orders. Livingstone's analysis balances genes and experiences in proposing explanations that illustrate commonalities between art and visual perception. Margaret Livingston's book, Vision and Art: The Biology of Seeing is an exception to this. Successfully linking art with visual. Harvard neurobiologist Margaret. Livingstone provides an art tour that many in the physics community will find fascinating. She begins, some-.

Language:English, Spanish, Portuguese
Published (Last):23.01.2016
Distribution:Free* [*Registration needed]
Uploaded by: LUCRECIA

53525 downloads 111572 Views 38.62MB PDF Size Report

Vision And Art The Biology Of Seeing Pdf

Vision and art the biology of seeing pdf. Vision and Art: The Biology of Seeing Margaret Livingstone Publisher: Abrams Release Date: ISBN. on how our visual processing system affects our perceptions of art. when the was simpler to overlay color vision and .. Vision and Art: The Biology of Seeing. 1 Vision and Art - The Biology of Seeing by Margaret Livingstone Chapter Television, Movies, and Computer Graphics All that I have said about the.

Yellowish-green light, for example, stimulates both L and M cones equally strongly, but only stimulates S-cones weakly. Red light, on the other hand, stimulates L cones much more than M cones, and S cones hardly at all; blue-green light stimulates M cones more than L cones, and S cones a bit more strongly, and is also the peak stimulant for rod cells; and blue light stimulates S cones more strongly than red or green light, but L and M cones more weakly. The brain combines the information from each type of receptor to give rise to different perceptions of different wavelengths of light. The opsins photopigments present in the L and M cones are encoded on the X chromosome ; defective encoding of these leads to the two most common forms of color blindness. The OPN1LW gene, which codes for the opsin present in the L cones, is highly polymorphic a recent study by Verrelli and Tishkoff found 85 variants in a sample of men. X chromosome inactivation means that while only one opsin is expressed in each cone cell, both types occur overall, and some women may therefore show a degree of tetrachromatic color vision. Color in the human brain[ edit ] Visual pathways in the human brain. The ventral stream purple is important in color recognition. The dorsal stream green is also shown. They originate from a common source in the visual cortex. Color processing begins at a very early level in the visual system even within the retina through initial color opponent mechanisms. Both Helmholtz's trichromatic theory, and Hering's opponent process theory are therefore correct, but trichromacy arises at the level of the receptors, and opponent processes arise at the level of retinal ganglion cells and beyond. In Hering's theory opponent mechanisms refer to the opposing color effect of red—green, blue—yellow, and light—dark. However, in the visual system, it is the activity of the different receptor types that are opposed. Some midget retinal ganglion cells oppose L and M cone activity, which corresponds loosely to red—green opponency, but actually runs along an axis from blue-green to magenta.

In television technology, at both the beginning and the end of the process-in the. However, in the intermediate stage of television-broadcasting and videotapes-colors are coded in a completely different way. The television broadcast color-coding system is surprisingly similar to the way our visual system handles color.

The human visual system first records an image as a three-cone signal and then converts it into a luminance signal plus two cone-difference signals, which are then transmitted to the brain. A television camera acquires three color images red, green, and blue of an image and in the intermediate stage broadcasting the imagecarrying part of the video signal consists of one luminance signal and two color-difference signals.

Why do our visual systems and television broadcasting share this similar approach of converting an RGB image into two color-difference signals and a luminance signal? The reasons may be analogous. I ll start with television. In RCA demonstrated the first television system.

The next year the Radio Manufacturers Association Television Allocations Committee realized it would have to divide up the usable ranges of the electromagnetic spectrum among all the groups that wanted to broadcast television. The group voted to allocate a range of 6 MHz per channel for this new technology. The bandwidth of each channel its frequency range had significant consequences for the television industry, because the bandwidth determines how much information can be carried in that channel.

The 6 MHz figure, of which 4. To do that for a Pixel-wide screen, you would need one-half Of times modulations in one-thirtieth of a second, which is 3. Considering that requirement, a 6 MHz bandwidth per station seemed, at the time, a generous allocation.

CBS immediately began working on developing color television, and by o had a working model of a smallscreen color television, which recorded, transmitted, and displayed red, green, and blue signals independently. There were two problems with this design. First, in order to broadcast images with as high a resolution as existing blackand-white televisions, it would need three contiguous 3. Second, only people with color television sets could receive the color broadcast signals, which were incompatible with the existing monochrome sets the public already owned.

After years of legal wrangling over standards for the color television industry, CBS was finally allowed, in , to broadcast its black-andwhiteincompatible color TV signal, but since hardly anyone could watch it, it was abandoned after less than four months.

Meanwhile, several groups, led by RCA, eventually did develop a black-andwhitecompatible color system. They did so by converting the three color signals red, green, and blue into a luminance signal red plus green plus blue and two color-difference signals red minus luminance and blue minus luminance.

The fact that the composite. One key insight for minimizing bandwidth requirements was the realization that a third green minus luminance color signal was unnecessary, because for every point in the image, you only need to know the sum of the primaries and the difference between any two of the primaries and the sum in order to know the value of the third primary.

This compromise standard, which is still used today, was settled on in By overlapping the signals slightly, engineers could still remain within the 6 MHz allocation. Incidentally, it is this overlap that makes busy patterns like stripes or checks look so weird on TV.

We still use this standard in this country, though it is now being phased out in favor of digital and high-resolution television. These images show the difference in resolution between the luminance signal and the color signals on a standard video or television display.

The top image was displayed on a computer monitor and was then recorded using a VHS video camera, which uses the same coding algorithm as television broadcasting. The resolution of the color signal, especially the blue, is lower than the resolution of the luminance signal in the bottom video image, even though in the original image the color and the luminance of the letters were equally crisp.

Video VHS , which must be compatible with television, is also coded in a luminance plus two color-difference signals. That is why you can t view videos on your computer monitor. When television is converted to a highresolution digital system, that will change.

Early mammals had a welldeveloped single-cone luminance, or blackand-white, visual system. When a second cone type developed later, initially it probably simply summed with the first cone type, serving to extend the range of the visible spectrum, so that animals could perceive wavelengths previously invisible to them.

Only when primates evolved and began expanding the visual system and using high-resolution object identification did the strategy of subtracting different cone types evolve, because color is another way, besides shape, to identify objects. At this point, evolution was at the same impasse as the television industry in the s. The new What system needed to be back-compatible with the already existing achromatic Where system. Also, primates still needed to be able to see the black-and-white images rods.

We haven t, yet, evolved a second low-luminance photoreceptor type so we can see colors at night. How can it be that television can tolerate so much less information in the two color-difference signals and 0.

The answer is that the Color part of our What system has a lower resolution than the Form part of our What system or our Where system, so a low-resolution color signal doesn t look as bad as a lowresolution luminance signal would. What s more, we tolerate especially low resolution in the blue-difference signal because our blue-yellow resolution is lower still than our redgreen color resolution; this is due to the fact that 1 percent of our cones are blue; 99 percent of our cones are red and green.

One manifestation of the low acuity of our color perception is that we don t even notice that the color part of the video signal in our television is much lower resolution than the luminance image.

Vision and Art - The Biology of Seeing by Margaret Livingstone

European television has had higher resolution rather than lines than American television because the European standards allocated more bandwidth for the video signal 5 MHz versus 4. For some time, engineers have been working on developing significantly higher resolution television, by at least a factor of two, so that television screens can be larger overall, and wider.

The American television industry s transition to this high-definition television HDTV -it hopes to phase out standard American TV in a few years-has been made possible by digitization of the signal and the use of compression algorithms.

The compression algorithms used in digital TV are of interest because they are similar to the strategies the human brain uses to extract information from the environment. These algorithms are so efficient that a station using them is now able to transmit four ordinaryresolution television shows or one HDTV show in its allocated 6 MHz bandwidth.

In JPEG, and in the visual system, regions of the image with high information content, such as edges, are signaled, but regions where nothing is changing are not. MPEG temporal compression involves coding an image along with the differences between successive images, which is similar in strategy to the visual sytem s strategy of coding the appearance of objects by the What system and their position and trajectory by the Where system.

Lecture Multimedia Data Video Date: Chapter 9: Perceiving Color Why do we perceive different colors? Color signals help us classify and identify objects. I know a banana is ripe when it has turned. Digital Image Processing Prof.

Color Color Vision 1 Review of last week Color Vision 2 Review of color Spectrum Cone sensitivity function Metamers same color, different spectrum Opponent black-white, blue-yellow, red-green Color spaces. Color Today! Sensing Color Coding color systems Models of Reflectance Applications 1 Color Complexity Many theories, measurement techniques, and standards for colors, yet no one theory of human color perception.

Introduction to image processing 1. An image is an array, or a matrix, of square pixels picture elements arranged in columns and rows. Figure 1: An image an array or a matrix.


Gross structure 2. Image continuity 3. Number of scanning lines 4. Color Perception Color vision is a key aspect of perceptual organization. It can be useful for detecting objects against a background.

Color is related to wavelength. The perceptual dimensions of color. David Bowdley This project has been funded with support from the European Commission. This publication reflects the views only of the author, and the Commission.

There are many different types. HDTV impact on video surveillance market 3 2. Development of HDTV 3 3. How HDTV works 4 4. The picture signal is. Computer Graphics Prof. Sukhendu Das Dept. Our early experiences with color mixing were blending.

Experiment 11 Color Observe and interpret the color sensations. Human visual perception - topics Visual acuity Weber-Fechner Law Lateral inhibition and excitation Transfer functions of the color channels Spatial and temporal masking Eye movements Bernd Girod: At times the energy acts like a wave and at other times it acts.

Part 1: Inside a CRT A: Cathode B: Conductive Coating C: Anode D: Phosphor Coated Screen E: Electron Beams F: Shadow Mask From: Estimated time for unit: Analog Television Two lectures of material Probably the single greatest human invention is television.

Although we may have some concerns about the content of what we see on TV -- the technology of TV.

Exercises Isaac Newton was the first person to do a systematic study of color. Circle the letter of each statement that is true about Newton s study of color. Refer Slide Time: Standards 7. Explain that human eyes respond to a narrow range of wavelengths of the electromagnetic spectrum.

Describe that something can be seen when light waves emitted or reflected by. Monitors and Graphic Adapters To the process of displaying the information a graphic adapter and monitor are involved. Graphic adapter: Introduction to Analog Video Prepared by: Color Image Processing What is color? Illumination Reflectance What is color stimuli? X Illumination Reflectance What is perceived. The amount of your eyeball covered by the fovea is just a couple of square millimeters—similar to the fraction of the night sky that appears to be covered by the moon.

Vision and art the biology of seeing margaret livingstone pdf

You can demonstrate this effect more simply by focusing on one of the words on this page while at the same time trying to make out other words to the right or left. You may be able to make out a word or two, depending on how far the page is from your eyes. But the area that you can see clearly is the area imaged on the fovea of your eye. Generally, you are not aware of the limitations of your peripheral vision.

You think that you have a clear view of the world because your eyes are always in motion. Wherever you look, you see a sharp, clear image. Interestingly, your peripheral vision is very sensitive to motion—a characteristic that probably had strong adaptive value during the earlier stages of human evolution. The photo below shows a typical distribution of data for this activity. Individual answers may vary.

Going Further This Snack is best with at least two people.

As the colored shape approaches the center of your field of view, the temptation to cheat and move your eyes to look at the object becomes nearly irresistible. A partner can watch you and stop the experiment when you give in to temptation and move your eyes to look.

They can now easily spot motions as subtle as one-hundredth of a pixel, which would normally be buried in noise. Their method is to mathematically transform images into configurations of sine waves. The researchers can therefore detect shifts in the positions of sine waves from one frame of a video sequence to the next, amplify these shifts, and then transform the data back.

When objects in the hidden region move, the light that they project towards the penumbra sweeps through different angles relative to the wall.

[PDF] Vision and Art: Biology of Seeing: The Biology of Seeing Ebook by KoryRitter - Issuu

These subtle intensity and color changes are usually invisible to the naked eye 3 , but they can be enhanced with algorithms. Primitive videos of the light projecting off of different angles of the penumbra reveal one person moving 4 and two people moving 5 around the corner.

Freeman et al. Like pinholes and pinspecks, edges and corners also restrict the passage of light rays. The leaves act as pinspeck cameras, each blocking out a different set of light rays. Accounting for parallax, the researchers can then piece these images together. This light-field approach yields far crisper images than earlier accidental-camera work, because prior knowledge of the world is built into the algorithms. In , realizing an idea he had five years earlier, Raskar and his team pioneered a technique that involves shooting laser pulses at a wall so that a small fraction of the scattered light bounces around a barrier.

By measuring the times-of-flight of the returning photons, the researchers can tell how far they traveled and thus reconstruct the detailed 3-D geometry of hidden objects the photons scattered off of behind the barrier. One complication is that you must raster-scan the wall with the laser to form a 3-D image.