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luzes cores e a visão humana
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by Affonso Beato, ASC ,ABC
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
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 particles - photons – quantum mechanics – quantum values - heat
• Light as energy – electromagnetic waves – electromagnetism - color
1.1 Light
• Light as particles - photons – quantum mechanics – quantum values - heat
• 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
natural sources
natural sources
natural sources
1.1 Light artificial sources
artificial sources
artificial sources
artificial sources
artificial sources
artificial sources
artificial sources
artificial sources
artificial sources
artificial sources
1.2 Color
1.2 Color electromagnetic frequency
electromagnetic spectrum
electromagnetic spectrum
electromagnetic spectrum
Color Formation
source x color x white light
source relation
Color Formation
Color Prism
Color Process
addictive process
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
Hue – color frequency
Saturation – color density
Color Terminology – H S I
• Primary
BLUE RED GREEN
Intensity – color intensity
Hue – color frequency
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
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
camera obscura – capturing an image
camera obscura – capturing an image
camera obscura – capturing an image
photographic camera analogy
photographic camera
motion picture film camera
motion picture digital camera