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From Light to Enlightenment

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From Light to Enlightenment sampling The sampling layer sampling background of spatial vision and color-vision (and the perception of dynamical phenomena) – PowerPoint PPT presentation

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Title: From Light to Enlightenment


1
From Light to Enlightenment sampling
  • The sampling layer
  • sampling background of spatial vision and
    color-vision (and the perception of dynamical
    phenomena)
  • isotropic and anisotropic detectors
  • sampling and color
  • sampling and meaning

Kees van Overveld
-1-
2
From Light to Enlightenment sampling
sampling of the light field
sea combat a metafor for sampling-as-reconstructi
on
the enemy playfield (reality)
containing the enemy fleet (things from reality)
my representation of the enemy playfield (the HVS)
results of my measurements (sampling) the enemy
playfield (measurements in the HVS)
the (sometimes wrong) hypotheses on the enemy
fleet based on my measurements (the mental
reconstruction of things in reality)
Kees van Overveld
-2-
3
From Light to Enlightenment sampling
sampling of the light field
finitely many samples to represent infinitely
much information errors (aliasing)
remedy low-pass filtering (make sure no
small-scale details are present)
Kees van Overveld
-3-
4
From Light to Enlightenment sampling
sampling of the light field
  • what constitutes visual sampling?
  • In the image plane (retina, ...) , light
    intensity is a function of
  • location (x,y),
  • time (t), and
  • wavelength (?)
  • being measured with detectors, each with their
    own footprint, both for x,y,t, and ? .

Kees van Overveld
-4-
5
From Light to Enlightenment sampling
sampling of the light field
furthermore detectors with a footprint in
sombrero-shape
Kees van Overveld
-5-
6
From Light to Enlightenment sampling
sampling of the light field
Kees van Overveld
-6-
7
From Light to Enlightenment sampling
sampling of the light field
Anisotropic filters are only sensitive for
intensity-transitions aligned with their own
orientation
Kees van Overveld
-7-
8
From Light to Enlightenment sampling
sampling of the light field
Properties of various types of detectors
two slightly different signals
sampled with a single broad footprint can not be
distinguished
sampled with multiple narrow footprints can be
distinguished
Kees van Overveld
-8-
9
From Light to Enlightenment sampling
What is 'seen' by which detector?
various footprints measure various aspects of a
distribution of color or brightness
Kees van Overveld
-9-
10
From Light to Enlightenment sampling
The size of the footprint perspective, distance
and scale
Kees van Overveld
-10-
11
From Light to Enlightenment sampling
The size of the footprint perspective, distance
and scale
Kees van Overveld
-11-
12
From Light to Enlightenment sampling
isotropic and anisotropic detectors
brightness and en color distributions
these are no 'mental images' rather, they
are outcomes of measurements in the sampling
layer, imposing constraints on a (re)constructed
mental image.
vertical transitions
horizontal transitions
borders in arbitrary direction
Kees van Overveld
-12-
13
From Light to Enlightenment sampling
visual aquity, contrast, and seeing details
Kees van Overveld
-13-
14
From Light to Enlightenment sampling
From physical spectra to the subjective sensation
of color
yields a representation of any spectrum in
precisely 3 'numbers' (measurements) let's say
X,Y,Z.
Kees van Overveld
-14-
15
http//www.artelista.com/en/artwork/25669436316899
89-colourful-fruit-composition-ii.html
16
http//www.artelista.com/en/artwork/25669436316899
89-colourful-fruit-composition-ii.html
17
From Light to Enlightenment sampling
Color space sampling spectra with three
different footprints
So any spectrum is interpreted as a collection
of three measured values
Kees van Overveld
-17-
18
From Light to Enlightenment sampling
Color space mixing (altering) colors by adding
or filtering
Kees van Overveld
-18-
19
From Light to Enlightenment sampling
Color matching assigning intersubjective
coordinates to subjective color
Kees van Overveld
-19-
20
From Light to Enlightenment sampling
From physical spectra to the subjective sensation
of color
  • Make X,Y,Z independent of intensity by
    normalizing
  • xX/(XYZ)
  • yY/(XYZ)
  • zZ/(XYZ)
  • consider a plane in x-y-z- space for zconstant

CIE-diagram
  • a straight line in XYZ maps to a straight line in
    xy (where did we see that before ...?
    Perspective!)
  • adding colors additively adding spectra in xy
    space linear interpolation
  • monochrome colors (rainbow colors) are on the
    border of a diagram you cannot go beyond since
    additon coefficients cannot be lt0
  • The red/violet line contains colors, not in the
    rainbow. These are mixed from two extreme rainbow
    colors

Kees van Overveld
-20-
21
From Light to Enlightenment sampling
Color space - an intersubjective 3D
representation of subjective colors
Kees van Overveld
-21-
22
From Light to Enlightenment sampling
3D color space alternative geometric
representations
Kees van Overveld
-22-
23
From Light to Enlightenment sampling
Consequences of CIE diagram
Each color (such as X) can be reproduced by
additive mixing of no more than two well-chosen
monochrome spectra (e.g. A and B or C and D) with
appropriate mixing ratios.
Kees van Overveld
-23-
24
From Light to Enlightenment sampling
Consequences of CIE diagram
Complementary colors are colors that, additively
mixed together, form white or grey. After images
are complementary there are neural correlates
for differences of primary colors Complementary
colors give maximal hue contrast. Distance to
white point saturation. Rainbow colors hence are
maximally saturated.
Kees van Overveld
-24-
25
From Light to Enlightenment sampling
Color illusions do we actually see colors or do
we estimate ?? (Retinex theory 1970-ies)
Kees van Overveld
-25-
26
From Light to Enlightenment sampling
From color spectra to subjective color sensation
  • Georges Seurat (1859-1891 pointillism)
  • painting on the 'sampling layer'
  • paradox approximate additive color mixing with
    colored paint

Kees van Overveld
-26-
27
From Light to Enlightenment sampling
Meaning at the sampling layer
Differences in locations above - below
Kees van Overveld
-27-
28
From Light to Enlightenment sampling
Meaning at the sampling layer
Differences in locations above - below
Kees van Overveld
-28-
29
From Light to Enlightenment sampling
Meaning at the sampling layer
Colors and their connotation in nature and culture
Kees van Overveld
-29-
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