Search results
Results From The WOW.Com Content Network
In photometric quantities every wavelength is weighted according to how sensitive the human eye is to it, while radiometric quantities use unweighted absolute power. For example, the eye responds much more strongly to green light than to red, so a green source will have greater luminous flux than a red source with the same radiant flux would.
Comparison of photometric and radiometric quantities. Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light.Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which characterize the light's interaction with the human eye.
Comparison of photometric and radiometric quantities Luminous flux (in lumens) is a measure of the total amount of light a lamp puts out. The luminous intensity (in candelas) is a measure of how bright the beam in a particular direction is.
If the measurement is adjusted to account only for light that reacts with the photo-sensitive surface, that is, weighted by the appropriate spectral sensitivity, the exposure is still measured in radiometric units (joules per square meter), rather than photometric units (weighted by the nominal sensitivity of the human eye). [5]
Comparison of photometric and radiometric quantities. Luminous intensity should not be confused with another photometric unit, luminous flux, which is the total perceived power emitted in all directions. Luminous intensity is the perceived power per unit solid angle.
Comparison of photometric and radiometric quantities. Radiance is useful because it indicates how much of the power emitted, reflected, transmitted or received by a surface will be received by an optical system looking at that surface from a specified angle of view.
Radiant intensity, a radiometric quantity measured in watts per steradian (W/sr) Luminous intensity, a photometric quantity measured in lumens per steradian (lm/sr), or candela (cd) Irradiance, a radiometric quantity, measured in watts per square meter (W/m 2) Intensity (physics), the name for irradiance used in other branches of physics (W/m 2)
For each photometric system a set of primary standard stars is provided. A commonly adopted standardized photometric system is the Johnson-Morgan or UBV photometric system (1953). At present, there are more than 200 photometric systems. [citation needed] Photometric systems are usually characterized according to the widths of their passbands: