Crossword clues for illuminance
Wiktionary
n. (context physics English) The luminous flux incident on unit area of a surface; measured in lux or lumens
WordNet
n. the luminous flux incident on a unit area [syn: illumination]
Wikipedia
In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance.
In SI derived units these are measured in lux (lx) or lumens per square metre ( cd· sr· m). In the CGS system, the unit of illuminance is the phot, which is equal to . The foot-candle is a non-metric unit of illuminance that is used in photography.
Illuminance was formerly often called brightness, but this leads to confusion with other uses of the word, such as to mean luminance. "Brightness" should never be used for quantitative description, but only for nonquantitative references to physiological sensations and perceptions of light.
The human eye is capable of seeing somewhat more than a 2 trillion-fold range: The presence of white objects is somewhat discernible under starlight, at , while at the bright end, it is possible to read large text at 10 lux, or about 1000 times that of direct sunlight, although this can be very uncomfortable and cause long-lasting afterimages.
Usage examples of "illuminance".
Thus a reflectance change shows itself as step edge in an image, while illuminance changes gradually over space.
By this argument one can separate reflectance change from illuminance change by taking spatial derivatives: High derivatives are due to reflectance and low ones are due to illuminance.
The luminance image can be considered to be the product of two other images‚ the reflectance image and the illuminance image.
This must mean that illuminance and reflectance images are not arbitrary functions.
The vertical spine appears to be a dihedral with different illuminance on the two sides.
Again, the configuration and gray levels suggest that illuminance is the cause.
Then, under a given illuminance, one would observe a distribution of luminance samples such as that shown in figure 24.