Autostereograms Convergence is on a point at the same distance as the images Boxes and faces are on the horopter How many boxes would you see? boxes and faces are on the horopter What would happen if you remove the divider of a stereoscope?

Autostereograms right-eye line of sight crosses left- eye line of sight in front of image (crossed convergence) each retina is now pointed at the opposite box How many boxes would you see? What would happen to the face? crossed convergence Now cross your eyes:

Autostereograms There would be three boxes middle box: right eye sees face shifted to right; left eye sees face shifted to left therefore: uncrossed disparity Face in the middle box appears behind square crossed convergence

Autostereograms Left Eye’s Image Right Eye’s Image Crossed convergence shifts right image to the right of the left image and vice versa:

Autostereograms What would happen if the convergence was uncrossed?

Autostereograms Left Eye Right Eye Uncrossed convergence shifts right-eye’s image to the left of the left-eye image and vice versa:

Autostereograms What would happen if the faces were switched relative to the boxes?

Autostereograms one doesn’t even need two different images!

RIGHT EYELEFT EYE Convergence tells your brain that the plane of the image is farther away than it really is Autostereograms Faces fuse

Autostereograms Uneven spacing between identical objects in a single picture can appear as disparity if the angle of convergence is inappropriate

Autostereograms Uneven spacing between identical objects in a single picture can appear as disparity if the angle of convergence is inappropriate TRICK: Seeing depth in autostereograms requires you to suppress the reflexive coordination between convergence and accommodation

RIGHT EYELEFT EYE If you uncross convergence, your right eye gets these faces shifted slightly to left, left eye gets them shifted to right = CROSSED DISPARITY Autostereograms Any repeating objects that have a spacing different from the background will have either crossed or uncrossed disparity What would you see?

RIGHT EYELEFT EYE If you uncross convergence, right eye gets these faces shifted slightly to right, left eye gets them shifted to left = UNCROSSED DISPARITY Autostereograms Any repeating objects that have a spacing difference from the background will have either crossed or uncrossed disparity What would you see?

Autostereograms by adjusting the disparity at different parts of the image (with a computer usually) one can make shapes that emerge or recede in depth

“Magic Eye” Stereograms Usually viewed with uncrossed convergence Imagine gazing farther than the surface (let your eyes “relax”) Now try to notice objects or forms in the blurriness As you become aware of shapes, try to focus (accommodate) the plane of the image without converging your eyes

Autostereograms

Wavelength and Color Recall that light is electromagnetic radiation

Wavelength and Color Recall that light is electromagnetic radiation Light waves have a frequency/wavelength

Wavelength and Color Recall that light is electromagnetic radiation Light waves have a frequency/wavelength Frequency/wavelength is the physical property that corresponds (loosely) to the perception called color

Color Vision Different wavelengths correspond roughly to the “colors” of the spectrum Wavelength and Color

Color Vision White light is a mixture of wavelengths –prisms decompose white light into assorted wavelengths Wavelength and Color

Color Vision White light is a mixture of wavelengths –prisms decompose white light into assorted wavelengths –likewise, adding all wavelengths together makes white light What happens if you mix several different paints together? Wavelength and Color

Color Vision Objects have different colors because they reflect some but not all wavelengths of light –the surfaces of objects are like filters that selectively absorb certain wavelengths Wavelength and Color

Color Vision Primary colors Perceiving Color What are the primary colors?

Color Vision Primary colors Perceiving Color Red Green Blue

Color Vision Primary colors Perceiving Color What makes them primary?

Color Vision Primary colors Every color (hue) can be created by blending light of the three primary colors in differing proportions Perceiving Color

Color Vision Primary colors Every color (hue) can be created by blending light of the three primary colors in differing proportions Led to prediction that there must be three (and only three) distinct color receptor types Perceiving Color

Color Vision Perceiving Color Four absorption peaks in retina: 3 cone types plus rods Absorption/Cone response

Color Vision Theories of Color Vision “Blue” “Green” “Red” Blue Wavelength InputCone Signal to Brain

Color Vision Theories of Color Vision “Blue” “Green” “Red” Green Wavelength InputCone Signal to Brain

Color Vision Theories of Color Vision “Blue” “Green” “Red” Red Wavelength InputCone Signal to Brain

Color Vision Theories of Color Vision “Blue” “Green” “Red” Yellow Equal Parts Red and Green = Wavelength InputCone Signal to Brain

Color Vision Theories of Color Vision “Blue” “Green” “Red” Yellow Equal Parts Red and Green = Wavelength InputCone Signal to Brain

Color Vision Theories of Color Vision “Blue” “Green” “Red” Yellow Equal Parts Red and Green = Wavelength InputCone Signal to Brain

Next Time: Color Vision Read Land Article for Thursday Feb 28th Go skiing