where does it say they compare to a 400? i thought they were only compared to 250 watt metal halide?

the par meter came in handy in comparing my previous fixtures par level to my LEDS, that way I underpowered them for a bit to help acclimate them to the levels my old fixture was at. Now I am fixing to surpass the level my MH/t5 fixture was at and only using 50% power. I lost a few frags but that was it, everything has seemed to acclimate well.... If i would have done it by eye, everything would have toasted...

So with that, I say the par meter definitely has a upside...