1.0 Light, Color and Human Vision

by Affonso Beato, ASC ,ABC

[email protected]

www.affonsobeato.com

© copyright 2011 Affonso Beato

version 01.14.14

1.0 Light , Color and Human Vision

1.0 Light

1.1 Light

The Origen – The Big Bang

1.1 Light

Principal Source

1.1 Light

• Light as particles - photons – quantum mechanics – quantum values - heat

1.1 Light


• Light as energy – electromagnetic waves – electromagnetism - color

1.1 Light


• Light as energy – electromagnetic waves – electromagnetism - color

• Visible Light as part of the electromagnetic spectrum

1.1 Light

• Light as particles - photons – quantum mechanics

• Light as energy – electromagnetic waves – electromagnetism

• Visible Light as part of the electromagnetic spectrum – Analog medium

• The Digital medium – Analog to Digital

• Light Field – plenotic cameras

1.1 Light natural sources

natural sources

1.1 Light artificial sources

artificial sources

1.2 Color

1.2 Color electromagnetic frequency

electromagnetic spectrum

Color Formation

source x color x white light

source relation

Color Formation

Color Prism

Color Process

addictive process

Primary colors - RGB

• Primary colors

BLUE RED GREEN

Color Process

addictive process

Color Process

• Primary • RGB

• Complementary • CMY

BLUE RED GREEN

CYAN MAGENTA YELLOW

Color Process

addictive process

Color Process

subtractive process addictive process

Color Process

subtractive process

1.3 Color Space

frequency and wavelength on RGB - Hue

Human vision luminosity response

chromaticity diagram – human gamut - CIE

2D chromaticity diagram – human gamut

ITU-709 Gamut on chromaticity diagram – human gamut

3D color diagram

3D color model

Color Terminology - H

• Primary

BLUE RED GREEN

Hue – color frequency

Color Terminology – H S

• Primary

BLUE RED GREEN


Saturation – color density

Color Terminology – H S I

• Primary

BLUE RED GREEN

Intensity – color intensity


Saturation – color density

electromagnetic spectrum in frequency and wavelength (Hue)

human vision latitude

RGB wavelength

color wavelength

Red 620–750 nm

Blue 450–495 nm

Green 495–570 nm

chromaticity diagram – human gamut

2D chromaticity diagram

Color Space comparison

ACES - Academy Color Encoding System

1.3 Color Space

• http://www.theasc.com/magazine/jan05/conundrum/index.html

1.4 Color color temperature

color temperature measurements

colormeter

color temperature

• sun behind a layer of hot air

1.5 Human Vision

1.5 Human Vision

• how it works

• visual sensitivity – quantity

• visual sensitivity to contrast (different lights levels) - quantity

• visual sensitivity to color – quality

• retinal persistence

• different color spaces

65

Image formation Exposure control Detection Processing

Cornea Lens

Iris Photoreceptor

sensitivity

Retina Rods Cones

Brain

Image formation

Human visual sensitivity

• range of 1: 100,000,000,000,000 cd/m2

1.5 Human Vision Human visual sensitivity

• The range from scotopic (rod) absolute threshold to a light level that can possibly cause damage covers a luminance range of about 14 log units. This is a range of 1: 100,000,000,000,000. At the lower end of this range the visual system trades color perception and good visual acuity for very high sensitivity to low light levels.

• Photopic (cone) threshold is almost 4 log units above rod threshold. Approximately the next 2 log units is called the mesopic range and it is here that both the rods and cones contribute to vision. The reader will notice that just inside the photopic range rod saturation begins. Rod saturation refers to the rods output not increasing as luminance increases. They are already responding as vigorously as they can.

• The beginning of color vision occurs in the mesopic range because of cone stimulation. Color vision reaches its best in the photopic region as does visual acuity. However, as luminance continues to increase, to very high levels, visual performance deteriorates. When the light energy is high enough it can cause retinal damage.

• From this description it would appear that the sensitivity differences between rods and cones explains the entire 14 log unit range of visual sensitivity. The time course of receptor sensitivity increasing in darkness and the role of the photopigments is understood. There is more to the story. Although we do not yet fully understand the whole story, more of it can be found in more on sensitivity.

Human vision workflow

1. Human vision

light > object> eye (lens + iris + retina as sensor/film ) > cerebral cognition (human monitor) > captured imagem

Iight and vision relations

camera obscura – capturing an image

Mozi (470 BC to 390 BC)

camera obscura – capturing an image

photographic camera analogy

photographic camera

motion picture film camera

motion picture digital camera

1.0 Light, Color and Human Vision

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