Steve,
Ummm...do you think you can do some of your PC measurements with a 3 feet distance from the lamp. Andy, from Icecap, did some measurements @ 3 feet.
From Andy :
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From IceCap:
The readings are in LUX.
Latest installment.
1)Two MagneTek Universal 446L electronic ballasts (2 lamps per ballast).
Wattage used by lamps and ballast = 173
Light meter reading from three feet away = 182
L/W = 1.052
2)One Model 660 electronic ballast.
Wattage used by lamps and ballast = 269
Light meter reading from three feet away = 333
L/W = 1.238
or 83% more light, 17% more lumens per watt.
All tests this time were on brand new G.E. AquaRay Fresh & Saltwater 4-foot, NO T-12 lamps. I ran the Conventional ballasts 1st just in case the break-in caused them to drop off output quickly.
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- Victor.