Version 0.10 (c) 2007 CELEST VISI N Star Light, Star Bright, Let’s Explore Light How You Perceive...
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Transcript of Version 0.10 (c) 2007 CELEST VISI N Star Light, Star Bright, Let’s Explore Light How You Perceive...
Version 0.10 (c) 2007 CELEST
VISINStar Light, Star Bright, Let’s Explore Light
How You Perceive Light
How many black dots can you count?
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DO WE SEE LIKE A CAMERA?
Unlike a camera, human vision is a perceptual process involving many parts of the brain.
or digital sensor
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What do we need in order to see?
A source of light
A source of reflected light
an eye to receive light
an eye to receive light
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When light falls on a surface, some of it is absorbed and some of it is reflected.
HOW DO WE SEE OBJECTS THAT DO NOT PRODUCE LIGHT?
reflected
absorbed
Our eyes can detect the reflected light.
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DARK AND LIGHT SURFACES
absorb most of the lightthat falls on them, andreflect little.
reflected
absorbed
reflected
absorbed
Dark surfaces Light surfacesabsorb little of the light that falls on them, andreflect most.
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HOW DO WE SEE THINGS IN THE DARK?
You can’t see in total darkness, because you need light to see.
However, you can see if there is a little light.But how?
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EDGE DETECTORS!
Vision is sensitive to the difference or contrast between two surfaces.
In terms of vision, contrast is the comparison between the reflected light of one surface and another.
A comparison is computed as a ratio of two measures.
How does contrast affect which owl you see in each picture?
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HOW DO WE KNOW WHAT IS GOING ON AROUND US?
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Vision, one of the five senses, controlled by specific types of cells, that send messages to a specific part of the brain.
Name the other four senses.
All of the senses are controlled by different types of cells that send messages to different parts of the brain.
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OUR FIVE SENSES LET US PERCEIVE THE WORLD
http://nanonline.org/nandistance/mtbi/ClinNeuro/agnosia.html
Smell and Taste
Vision Touch
Hearing
Back of head Front of head
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WHAT IS “PERCEPTION”?
Some perceptions are illusory.
Perception is the process of acquiring, “interpreting,” selecting, and organizing sensory information.
Do you always see what is “really” there?
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Are squares A and B the same shade of gray?
ADELSON’S CHECKERED SHADOW ILLUSION
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THE HUMAN EYE
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The eye is actually an organ in the shape of a ball. From the outside you can see the pupil and the iris. The pupil is what lets light inside the eye.
Pupil
Iris
The human eye is very complex
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Inside the Eye…
The lens directs the light to the retina at back of the
eye where the photoreceptors receive the light and
send information to the brain via the optic nerve.
THE HUMAN EYE
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Lens
Retina
Optic Nerve
Pupil
Iris
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VISION AND THE BRAIN
Light stimulates photoreceptors sending messages to the visual cortex.
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BASIC DEFINITIONSh
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REFLECTED LIGHT
Illuminant
Illuminance Luminance
Photoreceptors on the retina
Based on the diagram, define illuminant, illuminance, luminance,
and photoreceptor.