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  2. Orders of magnitude (illuminance) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude...

    40 lux: Fully overcast, sunset or sunrise 10 2: 1 hectolux < 200 lux: Extreme of darkest storm clouds, midday 400 lux: Sunrise or sunset on a clear day (ambient illumination) 10 4: 10 kilolux: 10–25 kilolux: Typical overcast day, midday 20 kilolux: Shade illuminated by entire clear blue sky, midday 10 5: 100 kilolux 110 kilolux: Bright ...

  3. Fluorescent-lamp formats - Wikipedia

    en.wikipedia.org/wiki/Fluorescent-lamp_formats

    Ballast-swap replacement for 4 ft T12 40 W T8: 1.0, 25: 8: 59 F96T8: Ballast-swap replacement for 8 ft T12 75 W single-pin T12: 1.5, 38: 4 "25" F40UTSL Retrofit replacement for 4 ft T12 40 W on underpowered residential-grade rapid start magnetic ballasts. These are F40CW lamps made with lighter cathodes that can only handle a lower amount of power.

  4. Candela - Wikipedia

    en.wikipedia.org/wiki/Candela

    The 26th General Conference on Weights and Measures (CGPM) redefined the candela in 2018. [10] [11] The new definition, which took effect on 20 May 2019, is: The candela [...] is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 10 12 Hz, [a] K cd, to be 683 when expressed in the unit lm W −1, which is equal to cd sr W −1 ...

  5. Luminous efficacy - Wikipedia

    en.wikipedia.org/wiki/Luminous_efficacy

    It is the ratio of luminous flux to power, measured in lumens per watt in the International System of Units (SI). Depending on context, the power can be either the radiant flux of the source's output, or it can be the total power (electric power, chemical energy, or others) consumed by the source.

  6. Standard illuminant - Wikipedia

    en.wikipedia.org/wiki/Standard_illuminant

    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.

  7. Lumen (unit) - Wikipedia

    en.wikipedia.org/wiki/Lumen_(unit)

    The lumen (symbol: lm) is the unit of luminous flux, a measure of the perceived power of visible light emitted by a source, in the International System of Units (SI). ). Luminous flux differs from power (radiant flux) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to ...