27 Nov 1997 ............... Length about 1,000 words (7,000 bytes).
This is a WWW document by Steve Draper, installed at http://www.psy.gla.ac.uk/~steve/courses/vision/numbers.html.
You may copy it. How to refer to it.
A Brief Organized List of vision science numbers
This document was taken from the internet, but in fact seems to be taken from
the inside cover of Wandell, Brian A. (1995) Foundations of vision
(Sunderland, Mass. : Sinauer Associates), with some additions of my own.
I have not myself checked most of the facts listed here.
N.B. "X^2" means X raised to the second power i.e. X squared. And "X^-3"
means X raised to the power -3 i.e. 1 divided by X cubed.
A "mu" means a micron i.e. 10^-6 of a metre (one thousandth of a millimetre).
- There are at least 10 fundamentally different types of eye (using
- Eyes have independently evolved between 40 and 60 different times.
- Radiometric units represent physical energy (e.g., radiance has units of watts
- Colorimetric units adjust radiometric units for visual wavelength sensitivity
(e.g. luminance has units of cd m^-2);
scotopic units are proportional to rod absorptions;
photopic luminance units are proportional to a weighted sum of the L and M cone
- Typical ambient luminance levels (in cd m^-2): starlight 10^-3; moonlight
10^-1; indoor lighting 10^2; sunlight 10^5; max intensity of common CRT
- One Troland (Td) of retinal illumination is produced on the retina when the eye
looks at a surface of 1 cd / m^2 through a pupil of area 1 mm^2.
- Lens focal length: f (meters); lens power = 1/f (diopters)
- Conversion of linear units (X) to decibels: Y = 20 log10(X); change of 0.3
log10 units is a factor of 2, or 6 dB
- The eyes are 6 cm apart and half-way down the head
- Visual angle of the sun or moon = 0.5 deg At arm's length: thumbnail = 1.5
deg; thumb joint= 2.0 deg; fist = 8-10 deg
- Monocular visual field measured from central fixation: 160 deg (w) x 175 deg
Binocular visual field measured from central fixation: 200 deg (w) x 135 deg
Region of binocular overlap: 120 deg (w) x 135 deg (h)
- Range of pupil diameters: 1mm -8mm.
- Refractive indices: air 1.000; glass 1.520; water 1.333; cornea 1.376
- Optical power (diopters): cornea, 43; lens, 20 (relaxed); whole eye, 60
- Change in power due to accommodation, 8 diopters
- Axial chromatic aberration over the visible spectrum: 2 diopters
- Retinal area: 5 cm x 5 cm; 0.4 mm thick
- One degree of visual angle = 0.3 mm on the retina
- Number of cones in each retina: 5 x 10^6 ;
Number of rods in each retina: 10^8
- Diameter of the fovea: 1.5 mm (5.2 deg); rod-free fovea: 0.5 mm (1.7 deg);
foveola (rod-free, capillary-free fovea): 0.3 mm (1 deg); size of the optic
nerve head: 1.5 mm x 2.1 mm (5 deg (w) x 7 deg (h))
- Peak cone density: 1.6 x 10^5 cones/mm^2;
- Foveal cone size: 1-4 mu (diameter) x 50-80 mu (length);
extrafoveal cone size: 4-10 mu (diameter) x 40 mu (length)
- Size of rods near fovea: 1 mu (diameter) x 60 mu (length)
- S cone spacing (foveal): 10 arc min
- L and M cone spacing (foveal): 0.5 arc min
- Number of (L + M) cones / Number of S cones = 100
- 1.5x10^6 optic nerve fibers/retina
- Ratio of receptors to ganglion cells: in fovea 1:3; for whole retina, 125:1
- Area of entire cortex: 1.3 x 10^5 mm^2; 1.7 mm thick
- Total number of cortical neurons: 10^10; density: 10^5 neurons / mm^3
- Synapses: 5 x 10^8 synapses / mm^3; 4 x 10^3 synapses/neuron;
- Axons: 3 kilometers / mm^3
- Number of corpus callosum fibers: 5 x 10^8
- Number of macaque visual areas: 30
- Size of each area V1: 3cm by 8 cm
Half of area V1 represents the central 10 deg (2% of the visual field)
- Width of a human ocular dominance column 0.5-1.0 mm; width of a macaque
ocular dominance column 0.3 mm.
- Minimum number of absorptions for: scotopic detection 1-5;
detectable electrical excitation of a rod 1; photopic detection 10-15
- Following exposure to a sunny day, dark adaptation to a moonless night
involves: 10 minutes (photopic); 40 minutes (scotopic); change in visual
sensitivity 6 log10 units
- Highest detectable spatial frequency at high ambient light levels,
50-60 cpd; low ambient light levels, 20-30 cpd (cpd = cycles per degree of
- The contrast threshold (Delta L / L) for a static edge at photopic luminances
- Highest detectable temporal frequency: high ambient large field, 80 Hz; low
ambient, large field 40 Hz.
- Typical localization threshold: 6 arc sec (0.5 mu on the retina)
- Minimum temporal separation needed to discriminate two small, brief light
pulses from a single equal-energy pulse: 15-20 ms
- Stereoscopic depth discrimination: step threshold, 3 arc sec; point threshold,
30 arc sec
- Visible spectrum: 370-730 nm
- Peak wavelength sensitivity: 507nm (scotopic) and 555 nm (photopic)
- Spectral equilibrium hues: 475 nm (blue), 500 nm (green), 575 nm (yellow),
no spectral equilibrium red
- Number of basic English color names: 11
(White, black, red, green, yellow, blue, brown, purple, pink, orange, grey)
- Incidence of:
- anomalous trichromacy (3 colours, but a different 3 from the rest of
us), 10^-2 (male), 10^-4 (female);
- protanopia and deuteranopia (long and medium wavelength cones missing), 10^-2 (male), 10^-4 (female);
- tritanopia (short wavelength cones missing), 10^-4;
- rod monochromacy (rods only), 10^-4;
- cone monochromacy (one cone type only), 10^-5