A bulb's color isn't related to its brightness. 10k is close to the sun's color spectrum most of the day but the sun actually changes color spectrum from dawn to dusk. It starts very red, then turns yelowish and white, then bluish before reversing back to sunset.
In terms of brightness, the sun is brighter overall. I know I compare my MH 1900 PAR to the sun 1700 PAR but the truth is that my MH only hits 1900 in a small area immediately under the bulb ... maybe 8" x 8". It goes down to 1000 or even 800 at the edges.
The sun's 1700 is everywhere and so it looks much brighter. When I turn my MH on at noon, I can barely tell that it's on.
I plan to use the Apex to turn on the MH if the PAR drops under 1200 from noon to 8pm... basically to extend the photoperiod.
