quote:Originally posted by Untamed12
I didn't read it that way... The Dana Riddle test says...
"the 75-watt Solaris produced 89.4% of the PAR generated by the 250-watt XM 20,000K lamp."
He then goes on to suggest that the Solaris produces a higher % of PUR (photosynthetically USABLE Radiation). That is, a higher percentage of the Solaris light production falls between 400-550nm (approx 87% vs 82%). I think that just means that the Solaris would be more effecient at producing useable wavelengths without wasting energy producing non-usable wavelengths. (are non-usable wavelengths waste...or do they contribute to the "look" of the aquarium?)
If one buys into that point of view, then you conclude that the Solaris produces about 94.8% of the PUR of the MH system tested.
Exactly. But then you have to take into effect that the XM has an unneeded glass shield on it in that test, so that drops the PUR number downfrom 95% to roughly 80%.
Consider the fact that a 20K XM puts out roughly 50 Par, and according to Sanjay, PUR is generally pretty proportional to PAR in MH bulbs. If you put a shield glass on the XM 20K, that puts you at roughly 42 PAR. If the Solaris is 95% of that efficiency, that puts it at having equal PUR to a halide bulb that puts out 40 Par.