Midterm 2: Objects and color

What does early level vision accomplish?

Early vision is the first stages of visual processing- finds edges, contrast, orientations, colors, spatial structure.

What does middle level vision accomplish?

Happens after early vision- organizes visual features into structures so the brain can recognize objects and features. Uses Gestalt grouping

What does high level vision accomplish?

Takes the organized features and objects from middle vision and RECOGNIZE them, assign meaning understand the scene.

What are the Gestalt grouping rules? 

Proximity, similarity, common region, connectedness, closure, common fate, symmetry

Proximity example:

close things belong together, clustered dots

Similarity example:

SIMILAR things belong together, same-colored shapes

Continuity example:

smooth lines connect, flowing curves

Closure example: 

when the brain fills in gaps, broken circles appear complete

Common fate example:

Things moving together belong together, flock of birds

Symmetry example:

Symmetrical elements group (patterns) mirror-image shapes (patterns)

What do T-junctions signify? 

Forms a T shape and is when one line or edge ends in front of another one, signifies that one object is in front of another

What do Arrow-junctions signify? 

When 3 lines meet forming a a Y shape, appear at corners, important for 3D shapes and corners 

What is the difference between ‘what/perception’ vs ‘where/action’ streams?

The DORSAL stream is for the ‘where/action’ pathway and is tuned for action and interaction with objects.

The VENTRAL is the ‘what’/perception pathway and is tuned for object recognition.

The DORSAL and VENTRAL are the 2 visual pathways

What is Template-matching?

Method of recognizing objects by comparing incoming visual patterns to stored templates in memory

What is structural description theory?

Brain recognizes objects by identifying their basic parts (geons) and the spatial relationships between them

Why is it easier to judge upright faces vs. upside down?

The nuerons in the visual cortex are tuned for right side-up faces.

What is Prosopagnosia?

A neurological condition where one has the inability to recognize faces, regardless of normal vision and intelligence. You can see a face clearly, but you cant recognize whos face it is.

What are the basics of the electromagnetic spectrum?

The range of all types of electromagnetic radiation which is energy that travels in waves and moves through space at the speed of light.

-They differ in wavelenght’s (difference between wave peaks) and frequency (how fast the waves vibrate).

What is the ORDER of the electromagnetic spectrum?

(Longest to shortest wavelength/lowest to highest frequency):

1) Radio waves- very long wavelength, low frequency, low energy

2) Microwaves: wavelength is 1mm-1m, use is microwave ovens, Wi-Fi, radar

3) Infrared (IR): Wavelength is 700nm- 1nm, use is for heat sensing, remote controls, night vision

4) Visible Light: Wavelength is 400-700nm, and its use is what humans can see, its colors are violet (400nm) to blue to green to yellow to orange to red (700 nm)

5) Ultraviolet (UV): Wavelength is 10-400nm, its use is sunburn, black lights, sterilization

6) X-rays: Wavelength is 0.01-10nm, its use is medical imaging, security scanners

7) Gamma rays: wavelength is 0.01nm and its use is nuclear radiation, cancer treatment

-The visual spectrum ‘ROYGBIV’ goes from 400-700

The basics of the Visual Spectrum:

The visual spectrum is the range of electromagnetic waves that the human eye can detect as light. We can only see a small slice of this (400-700nm).

Details/basics of the visible spectrum:

-Violet is the shortest wavelength and red is the longest wavelength

-Shorter wavelengths have more energy

-Longer wavelengths have less energy 

What did Newton show with his Prism?

He broke up white light into its components and went on to lay out the basics of additive color mixtures. He claimed that light that appears white is composed of a mixture of colored lights. (white light is made of all colors).

What is additive color mixture?

When different colored lights are combined and the result depends on the wavelengths of lights added together.

What aspects of color are physical (wavelength) and which are psychological (green)? 

-The PHYSICAL aspects of color are the wavelength, frequency, intensity (how strong/bright a light is), the mix of different wavelengths in the light. 

-The PSYCHOLOGICAL aspects of color are the hue (what we call the “color”), the saturation (how pure the color appears), the brightness (how light or dark the color appears). 

What does Spectral Reflectance Functions show?

Shows the relative amount (%) of reflected light for each wavelength.

What does Spectral Power Distributions show?

Shows how much power/energy light contains at each wavelength

The basics of color constancy: 

-Color constancy is the visual systems ability to perceive the true color (reflectance) of surfaces even when the illumination changes

-Its useful because it lets us perceive the world reliably even under changing light conditions

What is trichromacy?

The principal that human color vision is based on 3 types of CONES

Why are humans trichromatic?

To detect a wide range of colors

How is trichromacy used in devices screens? 

Devices have red, green and blue pixels which stimulate our S, M and L cones. Screens cause our 3 cone system to perceive a full spectrum of colors. 

What type of color vision do most mammals have?

They have dichromacy color vision based on 2 types of cones.

Whats the relationship between # of colors and # of cones?

The # of cone types determine how many independent color channels the visual system has, more cone types allow the brain to compare more signals.  

The spectral sensitivity function for cones:

To determine it, you measure a cones reaction to different wavelengths and it will have a wavelength that its most sensitive to. One is most sensitive to short wavelengths (blue), medium wavelengths (green) and long wavelengths (red).

What is color blindness?

When someone is missing a cone type, only having 2 types (missing an M or L cone).

Different creatures and different color ‘tuning’

Different creatures have different types and numbers of cones, changing the colors they see.