Report what happens when you look at the (actually) black and white form—does it appear to be faintly colored? If so, describe the colors you see, specifying where you see them.

Psych 463 Sensation & Perception

Dr. Swift

Sixth Assignment (Color)

1. Color Mixing. Use Project Lite, following directions at the end of the assignment. For each of the following, produce the specified color in the center of the diagram (i.e. where all 3 circles overlap), and report on the outputs of the three color guns. (In some cases you may wish to set a value of 0 for a given circle). Note that there is no single correct answer for any given color.

Color	R	G	B		Color	R	G	B
Red					Green
Pink					Greenish-Blue
Orange					Blue
Yellow					Violet
Yellow-Green					Purple

2. Cone Response and Perceived Color. Look at the following graph, noting that the dashed line is for rods and should be ignored. For each of the following, produce the specified color, and report on the relative outputs of the three cones (S, M, L) that go along with the following colors, noting that the output values are given on the Y axis. For the basic colors (e.g. yellow, green, blue) note that I have specified values close to a unique hue—i.e. one that does not appear to have any other color present.

Color	S	M	L		Color	S	M	L
Red (675 nm)					Green (500 nm)
Orange (610 nm)					Greenish-Blue (485 nm)
Yellow (575 nm)					Blue (460 nm)
Yellow-Green (550 nm)					Violet (440 nm)

3. Opponent Process System. Look at the slide from your Power-Point Presentation, reproduced below. Pick a wavelength in that matches the indicated color (i.e. is within the indicated range). Note that for Blue, Green and Yellow, you should be picking unique hues—i.e. ones that do not appear to have any other color. For example, do not pick a yellow that is slightly greenish or slightly reddish. For each of the following, indicate the relative output of (a) the Blue-Yellow mechanism (negative means blue and positive means yellow) and (b) the Red-Green mechanism (negative means green and positive means red). I have done 1 as an example.

Color	Wavelength	R/G	B/Y		Color	Wavelength	R/G	B/Y
Red (650 -675 nm)	655	+.25	+.10		Green (490-510 nm)
Orange (600-620 nm)					Greenish-Blue ( about 485 nm)
Yellow (580 nm)					Blue (460-490 nm)
Yellow-Green (540-550 nm)					Violet (about 420 nm)

4. McCollough Effect demonstration. Perform the basic experiment on yourself, adapting for at least two full minutes (five is even better).by going to the following web site:

http://lite.bu.edu/vision-flash10/applets/Color/McCollough/McCollough.html

a. Report what happens when you look at the (actually) black and white form—does it appear to be faintly colored? If so, describe the colors you see, specifying where you see them.

b. Tilt your head partially sideways (45 degrees) and report whether/how the colors change

c. Tilt your head fully sideways (90 degrees) and report whether/how the colors change

d. Explain what is going on, in (a), (b) and in (c)

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Directions for using Project Lite Color Package (related to Question # 1).

1. Go to

http://lite.bu.edu/vision-flash10/applets/Color/Addition/AdditionMove.html

2. Make sure that the numbers are visible on the Brightness slide bars, as illustrated below. If they are not, then you will have to press the download button at the bottom of the screen.

3. Do not press the “Controls” button, which allows you to adjust the Hue and Saturation settings. Only adjust the brightness settings.

4. Slide the controls to get the desired color at the center and note the values on all three controls.