On 27/11/2018 12:53, whisky-dave wrote:
On Monday, 26 November 2018 17:11:59 UTC, Fredxx wrote:
On 26/11/2018 16:45, whisky-dave wrote:
On Monday, 26 November 2018 16:28:32 UTC, The Natural Philosopher wrote:
On 26/11/2018 12:25, Tim Streater wrote:
A 5W LED produces most of the 5W as light. A 35W
light produces most of the 35W as heat.

No. the 5W LED still produces most of its output as heat.

I think its like 300mW of light in each case....



Light isn't measured in mW.

It can be very easily. Just count photons and their energy and you have
power.

But isn't even if you claim it's easy to count photons.
Perhaps this isn't why the SI unti of light isn;t the watt.



It gets confusing due to two types of efficiency there's also the efficiency of the amount of visable light compared to non visable (human eye).

That's sensitivity,

no it isn't.

Yes it is, I suggest you have a look at

and it you have 'white' light then the visible range
will already be determined.

wrong.

No I'm not. For low light levels, the response of the human eye changes.
However where colour is perceived the CIE standard curve is used to
convert radiant energy into luminous (i.e., visible) energy.

This might assist:
https://en.wikipedia.org/wiki/CIE_1931_color_space

https://electronics.stackexchange.co...cient-are-leds

This also mentions 'output power' and a max of 250 lumens/watt, on a
100% conversion of energy to light.

but only for that product.

No, it's the maximum for any product that produces a nominal white light:
https://en.wikipedia.org/wiki/Luminous_efficacy

Suggests white light is a max 251lm/W If further truncated to remove
wavelengths the eye is least sensitive to you can get up to 348lm/W