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An optical power meter (OPM) is a device used to measure the power in an optical signal. The term usually refers to a device for testing average power in fiber optic systems. Other general purpose light power measuring devices are usually called radiometers , photometers , laser power meters (can be photodiode sensors or thermopile laser ...
Use of a light meter for portrait cinematography in a Turkish music video set. A light meter (or illuminometer) is a device used to measure the amount of light.In photography, an exposure meter is a light meter coupled to either a digital or analog calculator which displays the correct shutter speed and f-number for optimum exposure, given a certain lighting situation and film speed.
In photography, exposure is the amount of light per unit area reaching a frame of photographic film or the surface of an electronic image sensor.It is determined by shutter speed, lens f-number, and scene luminance.
Wattmeter measures the electrical power circulating in any electric circuit; Microwave power meter measures power in a microwave signal; Optical power meter measures power in an optical signal; Google PowerMeter is a tool to track a household's energy usage; A cycling power meter measures the power output of a bicycle rider; Health meter, a ...
The definition tells us that 1 watt of pure green 555 nm light is "worth" 683 lumens. It does not say anything about other wavelengths. Because lumens are photometric units, their relationship to watts depends on the wavelength according to how visible the wavelength is. Infrared and ultraviolet radiation, for example, are invisible and do not ...
In photometry, luminous flux or luminous power [citation needed] is the measure of the perceived power of light. It differs from radiant flux , the measure of the total power of electromagnetic radiation (including infrared , ultraviolet , and visible light), in that luminous flux is adjusted to reflect the varying sensitivity of the human eye ...
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An exposure meter may not always be available, and using a meter to determine exposure for some scenes with unusual lighting distribution may be difficult. [4] However, natural light, as well as many scenes with artificial lighting, is predictable, so that exposure often can be determined with reasonable accuracy from tabulated values.