Talk:Luminous efficacy

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Luminous efficiency of a candle

The current recorded efficiency of 0.3 lm/W seems far too high and based on some questionable numbers used to calculate it.

The definition of a candela used to be based on a standard candle burning spermaceti at 120 grains per hour^[1]. This equates to approximately 85 watts of chemical energy which would almost entirely be converted into heat by combustion.

The total light output will be less than 4π as light emission will be strongest perpendicular to the long axis of the candle. Assuming the flame is a long infinitesimaly thin cylinder, the total emission will be 8/3π as there would be no light emitted at all verticaly, 1 candela emmitted horizontally and varying sinusiodally inbetween. In reality this would be modified due to light emitted upwards due to the thickness of the flame but also light absorbed beneath by the candle wax and so exact output would depend on the construction of the candle.

Either way approximately the total light output will be very close to 0.1 lm/W. — Preceding unsigned comment added by 2A03:1B20:7:F011:0:0:0:A01D (talk) 15:02, 28 December 2019 (UTC)[reply]

I removed the candle from the list altogether. You have successfully disputed the value that was given previously, but have not provided a reliable source to support a new value. Your calculation is original research, which we can't use. --Srleffler (talk) 18:48, 31 December 2019 (UTC)[reply]

References

^ https://en.wikipedia.org/wiki/Candela

Temperature of maximally luminously efficient non truncated black body radiator?

Did anybody calculate the temperature of the maximally efficient non-truncated black body? The graph in the article seems to suggest that it should be around 6700 K, but is there a source for a fairly exact value? If so, please add it. -- 2A02:3030:402:4548:8058:2F75:9CFF:DBC7 (talk) 10:05, 12 July 2022 (UTC)[reply]

Color LEDs

Can we (maybe me) add the efficacy of some colored LEDs? Gah4 (talk) 08:43, 26 November 2022 (UTC)[reply]

luminous intensity

The article doesn't mention much luminous intensity. That is, how to measure sources that don't emit equally in all directions. Some sources are measured in candela for that reason. Gah4 (talk) 08:09, 27 November 2022 (UTC)[reply]

[1] ttps://en.wikipedia.org/wiki/Candela

[1]