@ComputerSaysNo
"if you look at grow lights, the measured results are usually way lower than what the manufacturers report."
no one stated that the usable ppfd isnt lower then the manufactorer reported data, the same is true for your philips bulb.
of course its ppfd what counts in the end, but if you compare same spectrum leds to each other (bulbs vs. strips)
and only have the lumen per watt ratio given you can derive the ppfd from this (known spectrum given).
or, what will make you think that your philips bulbs magically put out more ppfd then they normally could according to the manufactorer data?
"To push to actual 2.6 umol/J, red LEDs are probably necessary, in any case only the most expensive lights feature such numbers. If it was easy to squeeze out that much efficiency just by optimizing the drivers,
everybody would be doing it. They all use pretty much the same LEDs (usually Samsung)."
were only trying to tell, that you get more usable ppfd out of led strips then you get out of led bulbs, you bring up ready made grow lights and 660nm reds and assume the rest.
you can push 2.6 with white leds only, just take enough of them, drive them low, and not all lights use samsung leds, especially not the low end grow light you brought to the table.
some of the very cheap grow lights use inferior driver concepts, use bad leds and drive them too hard (like your bulbs), to save the last penny.
i was just saying that you easily get more usable ppfd then 1.8 out of cheap led strips compared to the bulbs, apples to apples.
youre very limited which what you can achieve by using bulbs, as they usually drive the leds quite hard and their internal drivers are quite bad, (exept the dubai lamp maybe, which isnt 3€ at your doorstep).
so lets compare the philips bulb to the old bridgelux strip offered for 0.83 cent.
your bulb is 3.33€ on amazon.
the bulb is 1521 lm at 13W, 117 lpw.
a strip is 1205 lm at 7.7W and 156 lpw therefore.
so we need 2, gives 1.66€ vs. 3.33€.
half the price and more then 20% ppfd more output for less money.
the savings for the bulb holders almost compensate the price fo a quality driver, a cheap driver will be even less.
btw. electrical safety is way higer using a real led driver as a bonus for your lifetime.
and were comparing allready the best bulb vs. a very cheap strip here, recent strips goes up to 220, 240 lpw is doable with the newest stuff, more then a usable 2.6 achievable, easily., incl all losses, do the math.
edit: typos