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Block 9 > Mono: Photometry And Radiometry > Flashcards

Mono: Photometry And Radiometry Flashcards

(79 cards)

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1
Q

What is Radiometry?

A

Power produced by a source of electromagnetic radiation (does not take visibility into account)

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2
Q

What is Photometry?

A

Looks at the effect that radiation has on the visual system

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3
Q

What is the visual efficiency of detecting lights of different wavelengths?

A

Luminous efficiency function

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4
Q

What describes the relative sensitivity of the eye to different wavelength in the visible spectrum?

A

CIE luminosity function

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5
Q

What is the fundamental difference between photometry and Radiometry?

A

V(λ)

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6
Q

How would you describe the two colored lights below: Blue light: P = 10 W, λ = 400 nm; Red light: P = 10 W, λ = 600 nm?

A

Radiometrically equal but photometrically different

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7
Q

______ lumens/watt at 555 nm is the peak of V(λ)

A

680 lumens/watt

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8
Q

What is the luminous efficiency equation?

A

L x V(λ) x P

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9
Q

What is the luminous efficiency at 400 nm? Use the chart provided on slide 14 of lecture material

A

0 lumens

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10
Q

What is the luminous efficiency at 600 nm? Use the chart provided on slide 14 of lecture material

A

4216 lumens

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11
Q

Luminous efficiency is how many __________ a certain light source produces per __________?

A

Lumens

Watt

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12
Q

What is the luminous efficiency at 450 nm, 500nm, 550nm, 600nm, 650nm, 700nm for a 10 W source?

A

450 nm, - 0
500nm, - 2040
550nm, - 6800
600nm, - 4216
650nm, - 1020
700nm - 0

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13
Q

What is the luminous efficiency of polychromatic light?

A

14,076 lumens

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14
Q

Adding the lumens of each of the wavelengths to determine the total luminous power is __________ ______ ______________.

A

Abney’s Law additivity

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15
Q

RGB cones response from _______ - _______ nm

A

400 - 700 nm

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16
Q

RGB cones show a peak response at _______ nm

A

555 nm

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17
Q

Rods response from ______ - ______ nm

A

400 - 600 nm

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18
Q

Rods response with a peak sensitivity at _______ nm

A

507 nm

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19
Q

What is the peak luminous efficacy of Photopic Vision?

A

680 lumens/watt

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20
Q

What is the peak luminous efficacy of scotopic vision?

A

1700 lumens/watt

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21
Q

The eye is more sensitive to shorter wavelength light or higher color temperature source at what conditions?

A

Mesopic and scotopic

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22
Q

Radiometry describes ________ quantities

A

Physical quantities

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23
Q

Photometry describes __________ quantities

A

Psychophysical quantities

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24
Q

In optometry do we use photometry or Radiometry more?

A

Optometry uses photometry more than Radiometry

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25
Why is photometry used more than Radiometry in Optometry?
Because we are interested in measuring what people see where psychophysics applies
26
Radiometry is the measurement of what energy?
Optical radiant energy
27
Photometry describes _________ light only
Visible light only
28
What is the fundamental difference between the radiometric units and photometric units?
V(λ) function
29
What are the 4 Radiometry units?
Radiant power (w) Radiant intensity (I) Radiance Irradiance
30
Radiant Power is the total amount of _________ produced by a source per second
Energy
31
Radiant power unit
Watt
32
Radiant intensity is the amount of _________ produces by a source per second in a given ____________ by a point source
Light ## Footnote Direction
33
Radiant intensity units
watts/steradian (W/Sr)
34
Radiance is the radiant intensity per unit _________ and per unit _____________________ on a source
Area ## Footnote Projected solid angle
35
Radiance units
watts/steradian/m^2
36
What is irradiance?
Radiant power falling per unit area of surface
37
Irradiance units
W/m^2
38
What deals with the amount of light that reaches a given target?
Irradiance
39
What are the 4 Photometry units?
Luminous Power Luminous Intensity Luminance Illuminance
40
Luminous power is the total amount of light that emerges in ____________ from the source
All directions
41
Luminous power units
lumen (lm)
42
Radiant power is a function of how much ________ is present
Energy
43
Luminous power indicates _____________ ___________
Perceived brightness
44
Luminous intensity is the light power produced in a given __________ by a point source
Direction
45
Luminous intensity units
candela (cd)
46
Candela =
Lumen/Sr
47
1 lumen = ______ x _____
Cd x Sr
48
The amount of light coming off a surface in a specified direction is the ___________
Luminance
49
What is the perceived brightness of an extended source?
Luminance
50
Unit of luminance
nit
51
Nit =
1 nit = lm/sr/m^2
52
What is the luminous power that falls on a surface?
Illuminance
53
Unit of Illuminance
lux (lx)
54
Lux =
Lumen/m^2
55
What is a foot candle?
English unit of Illuminance
56
Foot candle =
Lm/ft^2
57
As an example: How will objects on a desk vary with illumination and luminance?
Objects on a desk may all have the same illumination but their luminance can vary
58
What is the measurement of light as perceived by the human eye?
Photometry
59
What is the measurement of color as perceived by the human eye?
Colorimetry
60
As a surface is moved away from a light source, the illumination of the surface:
decreases
61
inverse square law formula
E = I/d^2
62
For light coming from a point source and illuminating a surface, the Illuminance _____________ as it moves away from the source
Decrease ## Footnote Because the same number of lumens are spread out over a larger area
63
What happens to the area illuminated by one steradian if you double the distance?
Therefore if you double the distance d, the area E will increase by a factor of 4
64
A piece of paper is held 3 feet away from a point source of light with an intensity of 90 candelas. What is the resultant illumination on the surface of the paper?
3. 10 foot-candles
65
Does luminance depend on reflected light?
Yes
66
Amount of light reflected off a surface will depend on what 4 factors?
How much light illuminates the surface Distance from the light source Reflectance of the surface Tilt of the surface relative to your line of sight
67
Speculate reflector will reflect all the light how?
In one direction
68
How do surfaces that exhibit specular reflection look?
Shiny, like a mirror
69
Diffuse reflectors scatter light in ____________ directions
All
70
How do surfaces that exhibit diffuse reflection look?
Matte or dull
71
What is a Lambertian Surface or Cosine diffusers?
A surface that shows the same luminance from every viewing angle
72
The luminance of a Lambert surface = __________ x ___________
Reflectance Factor x illumination
73
What is the unit for retinal Illuminance?
troland (Td)
74
Retinal Illuminance is directly proportional to __________ and ___________
Object luminance and pupil area
75
Td = _________ x __________
Luminance of the object in nits x pupil area in mm^2
76
How does retinal Illuminance change with object distance? And why?
Remains constant for any object distance ## Footnote Because, while the Illuminance aka the amt of light entering the eye decreases with the square of the distance, the area of the retinal image also decreases with the square of the distance
77
Equation for pupil area
A=πr²
78
Suppose you are looking at a piece of paper in bright sunlight. What would the retinal illuminance be for the image of that paper on your retina, assuming the luminance of a piece of paper in sunlight is about 10,000 nits and your pupil diameter is equal to 2.0 mm?
Td = 31,400
79
Suppose you are looking at a visual acuity chart. What would the retinal illuminance be for the image of that chart on your retina, the luminance of a chart is ~5,000 nits and your pupil diameter is equal to 5.0 mm?
98,175 Td

Block 9 (6 decks)

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