Search results
Results from the WOW.Com Content Network
The lighting ratio is the ratio of the light levels on the brightest-lit to the least-lit parts of the subject; the brightest-lit areas are lit by both key (K) and fill (F). The American Society of Cinematographers (ASC) defines lighting ratio as (key+fill):fill, or (key+Σ fill ):Σ fill , where Σ fill is the sum of all fill lights.
Artificial light sources are usually evaluated in terms of luminous efficacy of the source, also sometimes called wall-plug efficacy. This is the ratio between the total luminous flux emitted by a device and the total amount of input power (electrical, etc.) it consumes.
The CU is the ratio of luminous flux from a luminaire incident upon a work plane to that emitted by the lamps within the luminaire. As a ratio, the coefficient of utilization is unitless. For example, some of the light emitted by a luminaire may exit away from the desired plane and is therefore wasted.
[1] [2] [3] The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and exposure of a photograph. [4] The f-number is dimensionless and is usually expressed using a lower-case hooked f with the format f / N , where N is the f-number.
Light from the sky can easily penetrate the upper storeys but not the lower, which rely primarily on light reflected from internal surfaces of the atrium such as floor-reflected light. [21] The upper stories need less window area than the lower ones, and if the atrium walls are light in color the upper walls will reflect light toward the lower ...
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
An ideal room would absorb all the light reflecting from a projection screen or emitted by a cathode-ray tube, and the only light seen in the room would come from the display device. With such a room, the contrast ratio of the image would be the same as the contrast ratio of the device. Real rooms reflect some of the light back to the displayed ...
Factor ()Multiple Value Item 0 0 lux 0 lux Absolute darkness 10 −4: 100 microlux 100 microlux: Starlight overcast moonless night sky [1]: 140 microlux: Venus at brightest [1]: 200 microlux