cs349 - s10 - Lecture 34
CS349 - Implementing User Interfaces - Spring 2010
Public Service Annoucements
- Assignment 4.
Lecture 34 - Display Properties
Eye & Brain
- cones gather light from a finte area
- cones are spaced by about 0.008 degrees in the fovea
At the optometrist
- 20/20 vision means being able to see a gap of
At the psychophysicist
The cone mosaic is not ordered, but random.
- phase processing is possible
- much finer resolutions, not limited by receptor size
- another order of magnitude in resolution.
Eye integrates over a temporal window about 30 msec long.
`Full Size' Displays
Serial versus Parallel Displays
Reflective versus Self-Luminous
- Reflective remove light
- digital paper, which is LCD with a mirror instead of a
- Self-luminous add light
- television is inherently self-luminous
- LCD removes light
- 4 pixels per millimeter (used to be three, etc.)
- At a distance of 700 mm this is 0.02 degrees.
- fine for television where viewing distance is longer
- high definition television: 1500 pixels per metre, 1.5 pixels
- 2 metre viewing distance 0.02 deg.
Apple Retina Display
- the display of the iPhone 4
- liquid crystal, backlit with LED backlight
- not OLED,
- Why? OLED about 10% efficient; LED close to 100% efficient: Apple
likes white backgrounds
- 3" by 2" (75mm by 50mm)
- 960 by 640 pixels
- 326 pixels per inch
- 13 pixels per mm
- "Apple engineers developed pixels so small, a mere 78 micrometers,
across that the human eye can't distinguish individual pixels."
- roughly 200 mm viewing distance
- pixel spacing is 0.022 degrees
- under optimal resolution we can resolve things down to 0.005 degrees
- At 200mm 0.005deg is 18 microns
- Viewing distance assumed above must be 800mm
- with hyperacuity the same test gives a viewing distance of 2400
Conservativism of photoreceptors
Human colour perception is a recent development
- and probably not too important for survival, at least for men
- on the X chromosome, so many men have colour vision defects.
Photoreceptor pigment mutated into three different molecules
- long ago yellow split from blue
- recently, among primates, yellow split into red and green