drdawg said: 
I replaced sixteen T-5 fixtures with eight T-5 HO fixtures and get double the light with half the fixtures.
That would mean an HO light puts out
four times the amount of light per unit length. That's not right: HO lights emit just under twice the amount.
http://www.lrc.rpi.edu/program... (See the table at the end.)
N.B. Since a lot of people won't know what HO means...... HO=High Output
