Today I measured the light intensity from my 55 watt AHS Bright light kits in my 45 gallon tank light fixture, for different reflector materials. To make this easier, I did the measurements with only one bulb of the two installed. First I checked the reflector with no modifications, using the same technique as I used for this fixture before. Next, I covered the AHS reflector with aluminum foil, trying to minimize the wrinkles in it. And, finally, I covered the reflector with white paper, spray painted with glossy white paint. All of the PAR measurements were taken at the fixture centerline, so the light was affected by the reflector, since that bulb was off center above the sensor.

I plotted all of the data, plus the data taken with both bulbs installed, on one graph:


Two obvious conclusions: I get about 50% more light at the center of the tank by using two light kits instead of one. And, aluminum foil and white paint are effective reflector materials, although not as good as the AHS reflectors. I think I may have misread the meter for the aluminum foil test at the closest to the bulb point. (I suspect all three readings for that location should be about the same, since almost all of the light is directly from the bulb with little from reflection.)

I'm out of ideas now for using the PAR meter to answer questions I have. But, if I think of something else I will try it.