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  2. Candlepower - Wikipedia

    en.wikipedia.org/wiki/Candlepower

    Candlepower (abbreviated as cp or CP) is a unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents. The historical candlepower is equal to 0.981 candelas. In modern usage, candlepower is sometimes used as a synonym for candla. [1]

  3. Luminous intensity - Wikipedia

    en.wikipedia.org/wiki/Luminous_intensity

    I e is the radiant intensity in watts per steradian (W/sr), y ¯ ( λ ) {\textstyle {\overline {y}}(\lambda )} is the standard luminosity function . If more than one wavelength is present (as is usually the case), one must sum or integrate over the spectrum of wavelengths present to get the luminous intensity:

  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. Metric system - Wikipedia

    en.wikipedia.org/wiki/Metric_system

    Candela is about the luminous intensity of a moderately bright candle, or 1 candle power. A 60 Watt tungsten-filament incandescent light bulb has a luminous intensity of about 800 lumens [ 29 ] which is radiated equally in all directions (i.e. 4 π steradians), thus is equal to I v = ⁠ 800 lm / 4 π sr ⁠ ≈ 64 cd .

  6. Luminous efficacy - Wikipedia

    en.wikipedia.org/wiki/Luminous_efficacy

    Luminous efficacy can be normalized by the maximum possible luminous efficacy to a dimensionless quantity called luminous efficiency.The distinction between efficacy and efficiency is not always carefully maintained in published sources, so it is not uncommon to see "efficiencies" expressed in lumens per watt, or "efficacies" expressed as a percentage.

  7. Candle - Wikipedia

    en.wikipedia.org/wiki/Candle

    The SI unit, candela, was in fact based on an older unit called the candlepower, which represented the luminous intensity emitted by a candle made to particular specifications (a "standard candle"). The modern unit is defined in a more precise and repeatable way, but was chosen such that a candle's luminous intensity is still about one candela.

  8. Luminous flux - Wikipedia

    en.wikipedia.org/wiki/Luminous_flux

    lumen per watt: lm/W: M −1 ⋅L −2 ⋅T 3 ⋅J: Ratio of luminous flux to radiant flux: Luminous efficacy (of a source) η [nb 3] lumen per watt: lm/W: M −1 ⋅L −2 ⋅T 3 ⋅J: Ratio of luminous flux to power consumption Luminous efficiency, luminous coefficient V: 1: Luminous efficacy normalized by the maximum possible efficacy See also:

  9. Talk:Foot-candle - Wikipedia

    en.wikipedia.org/wiki/Talk:Foot-candle

    1 candle-power to watts. 1 comment. 2 convert footcandles and lux to candelas. 5 comments. 3 calculating foot-candles with a camera. 2 comments. 4 Incorrect title? 1 ...