2. Vision

3. Vision Our most dominating sense (Visual Capture).
The eye is like a camera (it needs light).

4. Phase One: Gathering Light
The height of a wave gives us it’s intensity (brightness).
The length of the wave gives us it’s hue (color).
ROY G BIV
The longer the wave the more red.
The shorter the wavelength the more violet.

5. Getting the light in the eye

6. Structures of the Eye
Iris – regulates the amount of light going into the eye (colored part).
Pupil – black opening where light enters.
Lens – focuses light on the retina.
Retina – has layers of sensory cells:
Cones – (6 million) for color and daylight vision. Most highly concentrated near the fovea (back center of the eye).
Rods – (120 million) for peripheral and night vision. Located along the sides of the retina.

7. Mnemonic: Really Cool Babies Giggle Obnoxiously (RETINA: Rods, Cones, Bipolar Cells, Ganglion Cells, Optic Nerve)

8. Foveal Vision
To do a test close one eye, fixate on the upper line at the fixation point and try to read the words to the right and left without moving your eyes.
Visual acuity decreases with the distance from the fixation point.
Foveal vision works like a magnifier, peripheral vision is your data compression.

9. Vision: In the Brain
We have specific cells that see the lines, motion, curves and other features. These cells are called feature detector cells (Discovered by Hubel and Wiesel).
Goes to the Visual Cortex located in the Occipital Lobe of the Cerebral Cortex.
It’s here that we interpret what we are looking at.

10. Visual Pathway

11. Parallel Processing Color Motion Form Depth
The processing of several aspects of a problem simultaneously.
Color
Motion
Form
Depth

12. How do we see in color?

13. Facts on Color Vision
Colors we experience depend on the relative degree of stimulation to the cones.
Pigments mixed together absorb
more wavelengths than a single
pigment (subtractive color mixing)
Wavelengths added together
stimulate more cones (additive
color mixing)

14. Color Constancy
Perceiving familiar objects as having consistent color, even if changing illumination alters the reflected wavelengths.
A green apple for instance looks green to us at midday, when the main illumination is white sunlight, and also at sunset, when the main illumination is red.

15. What about when the context changes?
Because the brain computes the color of an object relative to its context, the perceived color changes.
ons/colourPerception/colourPerception.html

16. Young-Helmholtz Trichromatic Theory
Three types of cones:
Red
Green
Blue
These three types of cones can make millions of combinations of colors.
Does not explain afterimages or color blindness well.

17. Hering’s Opponent-Process Theory
The sensory receptors come in pairs.
Red/Green
Yellow/Blue
Black/White
If one color is stimulated, the other is inhibited.

18. Color Blindness Types of color blindness: Red / Green (most common)
Blue / Yellow
Total colorblindness
Most colorblind people are dichromats – they lack one kind of photopigment.
Males more likely to be colorblind.
Missing
Red
Missing
Green
Missing
Blue

20. Afterimages

28. Afterimages
When the eyes are then diverted to a blank space, the adapted photoreceptors send out a weak signal and those colors remain muted. However, the surrounding cones that were not being excited by that color are still "fresh", and send out a strong signal. The signal is exactly the same as if looking at the opposite color, which is how the brain interprets it.