1. Fundraiser Concert for Haiti U of L Students and Faculty Performing –9pm Blues Sen-sa-shun –10pm Shawna Romolliwa –11pm Dave Renter At The Slice, Friday Feb. 26 th –$5 for students, $10 for everybody else

2. Extra Credit for Participating in Experiments Go to www.tatalab.ca to sign upwww.tatalab.ca We are recruiting for a variety of experiments including basic perception and ADHD

3. Upcoming Gregory Article for today Read Pinker Article for help with stereo vision and stereo grams Read Land Article for March 2

4. Stereograms seeing depth requires “only” two different images on the retina this could be accomplished by an optical device that projects separate images into the two eyes

5. Stereograms Left Eye Right Eye Divider Right eye sees face to the right; left eye sees face to the left therefore: uncrossed disparity Face appears behind the square

6. Stereograms Left Eye Right Eye Divider What would you see?

7. Stereograms Left Eye Right Eye Divider Right eye sees face to the left; left eye sees face to the right therefore: crossed disparity Face appears in front of square

8. 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?

9. 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:

10. 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: Note the difference between convergence and disparity

11. 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

12. Autostereograms What would happen if the convergence was uncrossed?

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

14. Autostereograms one doesn’t even need two different images!

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

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

17. 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

19. 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?

21. 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?

23. 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

24. “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

25. Autostereograms

29. Wavelength and Color Recall that light is electromagnetic radiation

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

31. 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

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

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

34. 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

35. 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

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

37. Color Vision Primary colors Perceiving Color Red Green Blue

38. Color Vision Primary colors Perceiving Color What makes them primary?

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