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A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor coating in the lamp glow.
Typical photographic scene in full sunlight [7] [9] 7 kcd/m 2: Average clear sky [4] [5] [6] [12] 10 kcd/m 2: White illuminated cloud [6] 12 kcd/m 2: Fluorescent lamp [5] [6] 10 5: 75 kcd/m 2: Low pressure sodium-vapor lamp [6] 130 kcd/m 2: Frosted incandescent light bulb [5] [6] [12] 10 6: Mcd/m 2: 600 kcd/m 2: Solar disk at horizon [5] 10 7: ...
There is evidence that compact fluorescent light can worsen the condition. With the autoimmune disease lupus, exposure to compact fluorescent lamps will induce disease activity in photosensitive SLE patients. There is evidence that actinic prurigo is worsened by compact fluorescent light. This disease affects 3.3% of the general population.
The sun has a luminance of about 1.6 × 10 9 cd/m 2 at noon. [3] Luminance is invariant in geometric optics. [4] This means that for an ideal optical system, the luminance at the output is the same as the input luminance. For real, passive optical systems, the output luminance is at most equal to the input.
Luminous flux is often used as an objective measure of the useful light emitted by a light source, and is typically reported on the packaging for light bulbs, although it is not always prominent. Consumers commonly compare the luminous flux of different light bulbs since it provides an estimate of the apparent amount of light the bulb will ...
Full-spectrum light is light that covers the electromagnetic spectrum from infrared to near-ultraviolet, or all wavelengths that are useful to plant or animal life; in particular, sunlight is considered full spectrum, even though the solar spectral distribution reaching Earth changes with time of day, latitude, and atmospheric conditions.
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Illuminants A, B, and C were introduced in 1931, with the intention of respectively representing average incandescent light, direct sunlight, and average daylight. Illuminants D (1967) represent variations of daylight, illuminant E is the equal-energy illuminant, while illuminants F (2004) represent fluorescent lamps of various composition.