*I also put this in Hoppy's thread*
Just wanted to share the details of some recent PAR testing I did. I borrowed a PAR meter from my local club (Hoppy and Tom). I wanted to compare this to the light fixtures I had to see how reliable the information is, because we all know every fixture and light bulb is different. I think you'll see that PAR charts are meant to only be used as a rough guide. The only real way of knowing how much light you have is to test YOUR specific setup. There are way too many real world variables that will affect readings from one tank to the other.
Here's some important things you should know about my testing:
1. The Lowes and Current/Nova fixtures were tested on a standard 20g tank, with water. The sensor was placed in the middle of the tank, right under the fixture.
2. The Lowes & Current/Nova lights are 48" long, and the tank is only 24" long. To avoid having any stray light afftect the reading, I wrapped the overlapping section of the fixture with a towel. Removing the towels caused an increase of 4-5 micromols.
3. The Lowes fixture is black metal, even where the bulbs are. This is obviously isn't a good color for reflection, so I also wrapped the inside with aluminum foil and took more readings.
4. The Current/Nova fixture uses two bulbs, very close together. This has a very cheap thin aluminum reflector that goes over both bulbs.
5. The bulbs in the Lowes & Current/Nova fixture are fairly old, all over a year. Please keep this in mind as new bulbs may give a higher reading. The only bulbs that were brand new were the Giesemann bulbs in my Catalina fixture (3 days old at the time of testing).
6. I only took one reading with the Catalina fixture since it's mounted to a hanging bracket and the tank is heavily planted. I may try some more readings, but for the time being, it's just at 28". Also note that this is a 4-bulb fixture. I only tested 2 bulbs, in the outer most banks.
7. For the Current/Nova fixture, I had 3 types of bulbs. I took individual readings from each bulb and compared the results as seen below. Again, keep in mind that bulb age may be a factor. I did not go out and buy new bulbs to test this fixture.
Any questions please feel free to ask! I have a few more desktop lamps/fixtures that I will be testing in the days to come