Very technical, but maybe someone has some answers ?

LED lights. They are the latest thing, and have the remarkable advantages of low electricity usage and very long life.

I became aware of them when I saw my new car and checked things out. Then I bought three for my bathroom (lamps, not cars ! ) - a brighter light for shaving by replacing three 20 watt halogen bulbs ( life usually less than 1 year) with three 1.8 watt LEDs - life , said to be good for 30,000 hours of usage .
I reckon my bathroom lights are on for an hour a day, total. They should be good for 85 years or so . I am not Methusalah...but this eases worries about getting value from equipment before it wears out.

So that started me thinking about the lamps in my greenhouse, especially since LEDs are available in a range of specific colours for horticultural use. One lamp assembly has 1% emitting infra-red only, another percentage emitting at the red end of the spectrum ( all this for vegetative growth, and another percentage at the blue end, for flower production. Fantastic - especially if the running cost can be 10% of what it is now .
Then the problems start. With the conventional metal ballast sun lamps ( blue, red , or mixed spectrum - all of which look white to the naked eye, but warm white, cool white, etc. the lamp output is quoted in lumens ; 1 lumen = 1 foot candle = 10.74 Lux . And I know what lux I want on my leaves, I have measured it with a lux-meter on orchids in the wild.

One dealer said that frankly, you just have to experiment a bit. So I bought a couple of cheap 1 ft square mixed colours “growlight” panels. But after doing some experiments, I reckon my Lux meter is useless for determining the height above the plants to locate them, and also making guesses about how many lamps I need for a specific bench area ( they don’t seem to use lenses or reflectors btw ).

LEDs are not rated in Lumens. Instead they use quite unfamiliar units represented by acronyms such as PAR. One trail I followed up ended with an equivalence quote in mols - molecular weights...another dealer said he could give me umol figures, and when I pressed , he was clearly trying ( successfully) to blind me with science , but I gathered that he didn‘t understand it either.

So, HELP. Has anyone any experience ?