Does the dive light with high CRI be less efficient?

[XTAR]

Comparing with lumens, intensity, color temp, tint, CRI is the more subtle factor that affects the output of a dive light LED. The difference between high and low CRI might be virtually unnoticeable, unless comparing beams of the low and high CRI light next to each other. So how does the CRI affect the dive lights’ output? Some people think a light with high CRI LED comes at the price of efficiency.

Theoretically speaking, standard cool-white LED has the thinnest phosphor layer and convert the blue light mostly to green and yellow, which are the wavelengths that the human eye are most sensitive to. Thus you get high lumens per watt.

High CRI LED needs more broad spectrum, i.e. more orange, and especially more red. And human eyes are not very sensitive to red, which will cause more mismatch between spectrum and human eyes sensitive curve. So you get lower lumens per watt even if you have the same watts of light outputted after conversion in the phosphor.

Besides, the deep blue and deep red phosphor used in high CRI LED is less efficient, and more energy is converted into heat. And the phosphor layer is usually thicker which further reduces efficiency.

While, there are also people believe that any loss in efficiency between high CRI and standard cool white is more theoretical than practical. You really won't notice any dramatic differences between the two in normal use.

How about your views?

 

[Angelo Farina]

What you wrote is all correct. Getting higher CRI always diminishes slightly the efficiency in terms of Lumens/watt.
Same applies for color temperature: getting a "nice" color temperature, of, say 4500K (my favourite value) instead of 6000K necessarily involves more orange and red, hence lower efficiency.
Said that, my choice is always for a CRI of at least 90 and a color temperature not exceeding 4500K. It will be less efficient, which is absolutely not a problem for me. Quality wins over quantity...
There is a third factor to consider, that is uniformity of the luminous intensity within the beam. I do not like lamps which are brighter in the center and progressively dimmer on the sides. As a good light diffuser always comes with some loss, getting good uniformity is another design factor affecting overall efficiency.
And again, I favour an uniform beam with slightly less lumens.