Ooops…

• Before we go on…there are a few things I want to cover that we accidentally skipped over…..

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The Lens

Nearsightedness: A condition in which nearby objects are seen more clearly

than distant objects.

Farsightedness: A condition in which faraway objects are seen more clearly than near objects.

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Photoreceptors

E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969

Rods v. ConesRods•Black and white vision•Sensitive to light•Function well in dim light•Not good for color•Signal goes to one bipolar cell•Very sensitive

Cones•Color•Not effective in dim light•That is why it is hard to see color in rooms with dim light

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Bipolar & Ganglion CellsBipolar cells receive messages from photoreceptors (rods and cones) and

transmit them to ganglion cells, which are last before the the optic nerve.

Parallel Processing• The processing of several aspects of

an object simultaneously.

Color Motion Form Depth

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Parallel Processing

Processing of several aspects of the stimulus simultaneously is called parallel processing. The

brain divides a visual scene into subdivisions such as color, depth, form and movement etc.

Top Down or Bottom Up?• Processing that begins at sensory level is bottom up.• Processing that begins in the brain (through cognition…

thinking) is top down processing• Senses detect and minds interpret• So….what do you see immediately? What do you see if

you keep looking?

And Now…We Move On!

Color Vision

If an apple falls from a tree and no one hears it…does it make a sound???

If a tomato appears red…is it red?

No!! It is every color except red!

A tomato is NOT red because it rejects (reflects) the long wavelengths

of red

Light rays are not colored

Colors is in the “theater of our minds” and that is why we dream in color!

Why is her top green?Why is her top green?

Light has 3 Characteristics

1. Wavelength (hue/color)

2. Intensity (brightness)3. Saturation (purity)

Colors!• Hue (color) is the

dimension of color determined by the wavelength of the

light.• So…what colors you see are determined by

the wavelength• And a wavelength, by

definition, is the distance from the

peak of one wave to the peak of the next.• And…humans can

only see a small percentage wavelengths

This came form NASA…so you all are super-duper smart now…

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Intensity (Brightness)

Intensity Amount of energy in a

wave determined

by the amplitude. It is related to perceived

brightness.

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Intensity (Brightness)

Blue color with varying levels of intensity.As intensity increases or decreases, blue color

looks more “washed out” or “darkened.”

Trichromatic Theory

Three types of cones:• Red• Blue• Green• These three types of

cones can make millions of combinations of colors.

• Does not explain afterimages or color blindness well.

Opponent-Process theory

The sensory receptors come in pairs.

• Red/Green• Yellow/Blue• Black/White• If one color is

stimulated, the other is inhibited.

Afterimages

What color was the X on the white screen?

What color was the + on the white screen?

Opponent Process- Afterimage Effect

What color was the (whatever shape that was! LOL) on the white screen?

Color-Deficient Visionaka…color blindness

Genetic condition

Usually male People who

suffer red-green blindness have trouble perceiving the number within the design