Legibility

Question 1

Legibility

Answer 1

Users’ ability to read and discriminate the shapes of the symbols in the graphic.

Question 2

Luminance contrast

Answer 2

Brightness difference between symbols and their backgrounds. A
symbol with the same luminance as its background will usually
be illegible. Get adequate luminance contrast.

Question 3

Large hue differences between the text and background
are enough to overcome insufficient luminance
contrast.

Answer 3

F

Question 4

• Blue primary
  – Pure blue should not be used for fine detail or
  background
  –
• Visual resolution of fine detail is poor for blue. There are
  fewer blue receptors than green or red in the human retina,
  and none at all in the central fovea, which is the point of
  highest acuity.
• Lens and aqueous humor slowly grow yellower, filtering out
  the blue wavelengths.
• Lens gets weaker with age. Blue is at one extreme of its
  focusing range.
  – Any graphics that differ from the background only
  in the blue primary will be hard to read.
  –
  – Yellow differs from white only in the absence of the blue primary, so they also make poor symbol/background combinations.
  – Blue can be used in most contexts if care is taken
  to achieve adequate luminance contrast
• Substitute black by white (or some other high luminance
  colour). Blue text on the white background is nearly as legible as the black text
• Use a pale blue (adding yellow light, increasing the
  luminance but decreasing the purity) on the black or
  outline the text

Answer 4

Nothing