Ch. 4: Photometry Flashcards
what does the photopic luminosity curve explain?
shows that certain wavelengths are more efficient at stimulating the visual system than others
what is concerned with the power produced by a source of electromagnetic radiation, irrespective of its effect on vision?
radiometry
what deals with the effect that this radiation has on the visual system?
photometry
is it possible that both a 400 nm and 600 nm patch of ligth emit the same radiant power? how about luminous power?
yes both can emit 10 W (radiant power)
but 600 nm emits more lumens than a 400 nm power.
what does Abney’s Law of Additivity describe?
luminous power for such a stimulus is determined by calculating the number of lumens produced by each wavelength and then adding these values together.
what is luminous intensity?
refers to the number of lumens produced in a given direction by a point light source
what is luminance?
the amount of light coming off a surface such as a piece of paper, in a specified direction.
what is illuminance?
refers to the luminous power that falls on a surface (illuminance is not affected by the surface on which the light falls).
is it true that luminance refers to the light coming off the surface and illuminance refers to the amount of light falling on a surface?
yes
what 2 test follow Abney’s law of additivity?
HFP and MDB
does incandescent source produce light through the excitation of individual atoms?
no. a luminescent source does
what is the task in HFP?
to adjust the radiance of the sample stimulus such that the flicker is minimized (once completed the standard and sample wavelengths are at equal luminance)
what is the task in MDB (minimally distinct border)?
to adjust the radiance of the sample so that the visibility of the border is minimized. end point is when border exists only due to chromatic contrast (luminance contrast has been eliminated)
what is a blackbody radiator?
a theoretical construct that has proven convenient for describing sources of electromagnetic radiation, including light sources
what is the term used to describe incandescent light sources?
color temperature (CT)
is it true that the correlated color temperature of a fluorescent light tube depends on the nature of the phosphor that coats the bulb?
yes
what is unique about long-pass filters?
they only transmit long wavelengths of light
T/F? in narrowband filters is it true that the smaller the half-height bandwidth the more selective the filter?
true
What is the unit for luminous energy?
lumen second (lm x s)
What is the unit for luminous flux?
lumen (cd x sr) = lm
What is the unit for luminous intensity?
candela (lm/sr) = cd
What is the unit for luminance?
candela per square metre = cd/m^2
What is the unit for illuminance?
lux (lm/m^2) = lx
What is the unit for luminous emittance?
lux (lm/m^2) = lx
