1. Our Color vision is Limited
Johnson Chapter 4
Our Color vision is Limited

2. Blind Spot
L R
1. Write “L” and “R” along the left and right edge of a paper
2. Close your left eye
3. Look at the “L” as you move towards and away from the paper
4. The “R” will disappear as you move

3. Comparison of Rods and Cones
Used for low light conditions
Very light sensitive
Loss causes night blindness
Low visual acuity
High visual acuity; better spatial resolution
Slow response to light, stimuli added over time
Have more pigment than cones, so can detect lower light levels
About 120 million rods distributed around the retina
One type of photosensitive
Used for high light conditions
Sensitive to only direct light
Loss causes legal blindness
High visual acuity; better spatial resolution
Fast response to light, can perceive more rapid changes in stimuli
Have less pigment than rods, require more light to detect images
About 6 million cones distributed in each retina
Three types of photosensitive pigment in humans

5. Vision is optimized for edge contrast, not brightness

6. Insensitive to brightness

7. Insensitive to brightness

8. Ability to discriminate colors depends on how colors are presented
Paleness
The paler two colors are, the harder it is to tell them apart

9. Ability to discriminate colors depends on how colors are presented
Pale color marking the current step makes it hard for users to see which step in the airline reservation process they are on.

10. Ability to discriminate colors depends on how colors are presented
Size
The smaller or thinner objects are, the harder it is to distinguish their colors

11. Ability to discriminate colors depends on how colors are presented
Size
The smaller or thinner objects are, the harder it is to distinguish their colors

12. Ability to discriminate colors depends on how colors are presented
Size
The smaller or thinner objects are, the harder it is to distinguish their colors
Text is often thin, so the exact color of text is often hard to determine

13. Ability to discriminate colors depends on how colors are presented
Separation
The more separated; the more difficult it is to distinguish colors

14. Ability to discriminate colors depends on how colors are presented
Separation
The more separated; the more difficult it is to distinguish colors

15. Color Blindness

17. External factors that influence the ability to distinguish colors
Variation among color displays
Grayscale displays
Display angle
Ambient illumination

18. Color Terms
Hue
Brightness
Saturation

19. Guidelines for using color
Distinguish colors by saturation and brightness as well as hue
View them in gray scale
Use distinctive colors
Avoid color pairs that color-bind people cannot distinguish
Dark red vs black, dark red vs dark green, blue vs purple, light green vs white
Use color redundantly with other cues
Separate strong opponent colors

20. AVOID

21. Introduction to Color Guidelines and Standards
Discrimination and identification
Luminance contrast
General problems of color design.

22. Guidelines for Color Discrimination and Identification
Use no more than six colors to label graphic elements
Use colors in conformity with cultural conventions
Red, yellow, and green are associated with safety status
Use color coding consistently across displays and pages.
Use color coding redundantly with other graphic dimensions

23. Guidelines for Color Discrimination and Identification
Don't use color coding on small graphic elements.
Use neutral background where color judgments are critical.

24. Luminance Contrast Color Guidelines
The minimum luminance ratio between symbols and background shall be 3:1

25. Luminance Contrast Color Guidelines
Pure blue should not be used for fine detail or background.
Blue has low luminance
Visual resolution of fine detail is poor for blue.
blue primary stimulates mostly the short-wave cones, which contribute little to the visual process that forms edges (like those that make up letters)

26. Other Color Design Guidelines
Use color sparingly, for specific purposes

27. Other Color Design Guidelines
Avoid overuse of saturated colors
Successive contrast is a result of looking at a patch of one color for a while, then looking at a different set of colors. The appearance of the second set is altered by the afterimage of the first color.