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That meter pins hard right (roughly 2500) outside in southern California full sun at noon in July. 2000 is the brightest shade possible - basically full sun and thin leaf cover if the wind rustles the leaves. As you'd imagine, the plants grow very much like they're in my yard, they're just smaller in size (3ft versus 12ft).
The cab you're looking at is 4ft wide x 2ft deep x and 4ft tall. I've recorded the light levels with this meter down the right wall when it was empty. If you look very closely at the brown panel about 2/3rds down the right side you'll see a "750" in black sharpie.
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When I first started growing in '08, I took this little light meter to all of my friends gardens with big lights. I tested canopy brightness of multiple light 5k setups, 1000w / 600w / 400w solo HPS, MH, CMH, etc. because I needed an idea of how bright my canopy needed to be.
As a general rule, the guys with 600w (non air cooled) were around 1000umol at center canopy on this meter, while the guys who had air cooled lights could run closer and were usually about 1300umol under the center of the bulb. My friends with 1000w or multiple 1000w bulbs ran 1400-1700umol under the bulb center, the latter being air cooled hoods.
Will cannabis produce bud at 800umol? Absolutely. You can see at the 750 mark (even shaded) the buds look great. The top of my canopy is at the 2000 mark and haven't really seen any issues, very occasionally I see bleaching in the buds. Normally, they just look like they were run at max tilt under big lights.
Boats N Hoes
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MAC1
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Love the cab set up and those plant look beautiful my man.
Meters and numbers and semantics aside, what you’re doin is obviously working real nice for you.