Perception / Action
Estimate interaction time :
Fitt’s law : Pointing time relies on D/W ( Distance to target / Width of target)
Solutions:
- Reduce D : Popup menus / Attract applications or target
- Increase W : The Mac bar (border is infinite) / Marking menus (rely on angle)
- Mouse gain : mouse moving speed
- Semantic pointing : Common actions easy to reach while dangerous hard
- Avoid Pointing : Hotkeys / Gesture
Hick law : Selecting time relies on n (number of the options)
Colors
Color models:
RGB : Additive model
Light emission (screens)
• R, G, B primary colors
• Each pixel has 3 subpixels
Match the wavelengths detected by the cones
Displays colors as we see them (not as they are!)
CMY(K) : Subtractive model
Light reflection (paper prints)
• Complementary colors: Cyan, Magenta, Yellow
Printers: CMYK : CMY + blacK
High-end printing (art books): 6 colors or more because of imperfect pigments
HSV
Equivalent to RGB but more closely align with how we describe colors
• Hue (teinte): primary color (wavelength)
• Saturation = proportion of secondary colors
• Value = brightness
Variant: HSL Model (different calculation of S and L (light))
CIE Lab
L: black to white a: green to red b: blue to yellow
sRGB (not a color model but a color profile配置文件)
• Color space created by Microsoft & HP • Often used as a standard profile • Used in CSS • Some limitations: modern devices may have a larger gamut
Golden Rule
• Contrast V (brightness) rather than H (hue)
• Use at least a brightness ratio of 1/3 (1/10 if possible) between the background and the foreground
• Human vision more efficient in the center of the spectrum (yellow, green)
• Color vision deficiency
Gamma correction
Problem: big difference between Luminance and Brightness • Luminance: measurable quantity of light • Brightness: perceived quantity of light Brightness = Luminance ^ n
Ergonomic criteria
- Guiding
- Workload
- Explicit Control
- Adaptability
- Error Management
- Homogeneity / Consistency
- Significance of Codes and Denominations
- Compatibility