lecture 4 photometry Flashcards
name the 2 ways one can quantify light
photometry and radiometry
photometry is the measurement of _____ _____
visible light
radiometry is the measurement of ____ _____ from ____ to ____
optical radiation, infrared to UV
cd/m2 (or foot-lambert) are the units of…
luminance (Lv) aka nits (luminous intensity per unit projected area of an extended source)
lm/m2 is the units of…
illuminance (Ev) aka lux (luminous power on a surface)
a steradian is a ____ from a ____
cone, sphere
radiometric equivalence of luminance (luminous intensity per unit projected area of an extended source) is…
radiance (W/sr/m2)
radiometric equivalence of illuminance (luminous power on a surface) is…
irradiance (W/m2)
a lumen is a unit of…
luminous power (lm)
a candela is a unit of….
luminous intensity (lm/sr) or cd
radiometric equivalence of luminous power (total light from a source) is….
radiant power (J/s) or W
radiometric equivalence of luminous intensity (light produced in a solid angle by a point source) is…
radiant intensity (W/sr)
lm/W is the unit for
luminous efficiency (how efficient our vision system is at detecting a source of a given luminous power
____lm/W is the number of lumens per watt that is maximally absorbed by the photopic system
683 lm/W
____lm/W is the number of lumens per watts that is maximally absorbed by the scotopic system
1700 lm/W
on a graph of luminous effciency vs wavelength (nm) you are given 10 watts @500nm, 500nm corresponds with 0.4 on the luminous efficiency axis, what are lumens?
lumens=(lum eff)(683 lm/W)(W)….lumens = 0.4 x 683 x 10=2732 lumens
What law describes adding all lumens from all wavelengths to get the total
Abneys law of additivity…. (scotopic and photopic can also add together)
true or false: luminance is the same as brightness
false, brightness is percieved and can be percieved differently.
true or false: an example of illuminance is the lit part of a table where a flashlight is shining
true
true or false: an example of luminance is the light in motion moving away from its source
true
which law describes: the energy twice as far from a source is spread over 4 times the area, reducing intensity by 4 times
the inverse square law..(also if you move 3 times as far the intensity reduces by 9 times)
true or false: a troland (td) is is a unit of measurement equivalent to luminous intensity (cd) incident on the pupil
true
in additive color mixing, blue + green + red make…
white
in subtractive color mixing, cyan + magenta + yellow make….
black
in subtractive color mixing, cyan + yellow=____, cyan + magenta =_____, magenta + yellow=____
green, blue, red
in additive color mixing, red + blue=____, green + blue=___, red + green=____
magenta, cyan, yellow
what kind of filter would I use if I wanted to isolate a light between 510nm and 530nm?
a bandpass filter
What kind of filter would I use if I wanted to block 10% of light equally across the spectrum?
neutral density filter
what kind of filter would I use if I wanted to filter out infrared light?
IR filter
What kind of filter would I use if I wanted to allow everything below infrared to pass thru?
a cut filter
what kind of filter would I use if I wanted to allow long wavelengths of light thru but not short wavelengths?
a longpass filter
The cornea and lens work together to create what kind of filter?
a longpass filter to filter out UV
