Exam 1 Flashcards
Reflection
the vibrations of the surface electrons do not pass their energy down through the material
-incident light goes back at the same angle it hits
process by which photons arriving at the surface of a material change their direction of travel on impack and return
Reflectance factor curves
What is being reflected back from the surface when light hits it
• A black body is an idealized physical body that —absorbs all incident electromagnetic radiation and re-emits energy indiscriminately over a wide energy band
-All normal (baryonic) matter emits electromagnetic radiation when it has a temperature about absolute
Transmission
transparency occurs because of the transmission of light waves through an object
- an object looks transparent because light waves pass through unchange
- frequency DOESNT change when the vibrations pass from one atom to another (ex. glass to water, glass to air)
Color
sensation caused by certain qualitites of light that the eye recognizes and the brain interprets- an experience
in the LIGHT SOURCE not the object (light activity)
Construction of the eye
Light from all portions of the field of view enters the eye through the pupil and is focused on the retina the number of photons passing through the lens is controlled by the iris which forms a circular opening
Ration is 1:15 when small and large
The light streaking the retina is absorbed and converted into physiological message that is transmitted from the retina through a complex network of nerves to the brain
In the brain the message is interpreted to result ultimately in our perception of the world
Eye is held in place with 6 . muscles
The cornea forms the outer surface of the eye and acts as protective shield
Lens is made of elastic tissue
By a process of refraction focuses on image of what the person is look at inform of streams of photons on the retina
Central portion of the image is focused on the more sensitive area of the retina, the fovea
Controlled change of the shape of the lens by automatic muscle action allows sharp focusing on object nerby or
Retinal receptors
120,000,000 photosensitive cells- rods and cones
Spectral sensitivities of retinal receptors
If the intensity of light is increased, the magnitude of the same hue would be perceived as lighter
-The lighter shade of color needs more light- deflect more light
color blindness
- more females are color blind
- issue with how the cones perceive wavelength
- Ishihara test: subject reads number or shapes of dots
- fransworth-munsell: subject tries to arrange hue chips in a progression of red to blue (100 hues)
Munsell System
How it works:
Munsell color system is a system based on equal visual perception with 1450 chips, each is designated by a page number, lettering to show what color, value 1-10 and saturation 1-anything
Properties of color described:
- 1450 colors in 40 hues
- describe in hue, balue, chroma
How to interpret/calculate numerical descriptors:
-expressed by a # and letter
-letter is the hue: red, blue, yellow, green, purple or adjacent pair (green-yellow)
-number from 1-10 for value
-begin with page number
-ex. Page 2 of green yellow, value 7, chroma of 8
2GY7/8
application/uses:
advantages:
- agreement to equal visual perception
- notation is not linked or limited to existing samoples
- any conceivable color can be fit into the system
- system can match each book closely
disadvantages:
- Subject to light, fade, factory chemicals, finger prints
- may be made of different colorants and dont always match
CIE System
How it works:
Properties of color described: defined the spectral power distribution of four standard illuminats and established the spectral color matching functions of a standard observer
maps the physical wavelength to perceived color based on a standard observer. by shining 3 colored lights R,B,G and white - lumminants on a white board to create a spread
How to interpret/calculate numerical descriptors:
Values based on the amount of each color light RBG
application/uses: color matching
advantages:
- represent a wide range of color\
- y with line = exactly the same as the eyes response curve to the total amount of power
- y=spectral luminous efficiency therefore tristimulus value Y indicates the color lightnes, regardless of anything else
disadvantages:
- no physical sample
- no provision for black
- color differences are not clearly established
Systems based on Physical samples
How it works: random arrangements ex. color card for paint
Properties of color described:
How to interpret/calculate numerical descriptors:
application/uses:
advantages:
disadvantages:
you cannot deduce the intermediate colors
CIE illuminants
- Source A
□ A typical incandescent light (color temp 2854 degree K) - Source B
□ Direct sunlight at noon (4800 k)
-Source C
□ Average daylight from the total sky
® Overcast 6500
-Source D
□ A close representation of daylight
Source with highest degree is the bluest
CIE standard observers
- A representative of the average color vision of the human population
- A test lamp is shined on a white screen and Is matched by the combination of three colors red, blue, and green
Transverse Waves
need a medium - ex. a ripple in a pong
Longitudinal wave
the disturbance causes the medium to be displaced back and forth in the same direction the wave is traveling
ex. sound
Hue
- traditional color name of a specific wavelength of light
- it distinguishes one spectral color from another
Brightness
sensation of overall intensity of light
- higher intensity is brighter
- lightness is used for the surfaces of objects
lightness
○ Related to the % of incident light reflected by a surface and refers to the blackness, grayness, or whiteness
Lightness is related more closely to the surfaces ability to reflect light than to the properties of the light actually entering your eye from that surface
Rods
can work in low light, but can not resolve sharp images or colors
-chemical for vision signals:
Rhodopsin: when it absorbs photos it undergoes a molecular change triggering a response in the rod cells
-absorb energy 400-510 nm
Cones
Can resolve sharp images and color but require higher light levels
- 3 types of cones:
- red: sensitive to red light
- blue
- green
- equal stimulation of all 3 produce white light
- 7,000,000 cones located in the fovea
Vision
- The information created in the rods and cones by photons passes through the connecting cells and is funneled out of the eye by the optic nerve
- The optic nerve exists from the retina creating a circular blind spot in our field of vision
example (3 types of cones- young theory): How do we see Yellow?
○ A pure yellow light of a single wavelength would stimulate the red receptors and green receptors, so woulda mixture of a red and green light
In both cases we see yellow
Tetrachromat
fourth cone for green and red
Saturation
-corresponds to the purity of color
-NOT the intnsity
an unsaturated color would have contributions from many other color wavelengths
-mono chromatic have the highest saturation
