Quote:
Originally Posted by Myka
You're comparing grapes to raisins. 8 bulbs x how many watts? 54w? That is 432 w (quick math I hope that's right haha). You can't compare 432w of T5 to 250w of halide! That's not a fair comparison. PLUS, you have to use the same Kelvin bulbs in order for it to be accurate. According to Steve (Stir Crazy) actinic bulbs put out a false high PAR reading as well, so if you have actinics in your 8 bulb fixture you're not getting an accurate reading.
In order to compare T5 to MH you need to make sure all the variables are equal...this is where a lot of people fail, and come up with misleading numbers which they now think is the be all end all.
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If you're going to calculate the T5 as if it's going on a 4 foot tank (54W) then you also need to be reasonable about the application of the MH - no one is going to try to realistically light a 4 foot tank with a single 250W MH. So consider that the above example is likely 2 x 250W MH in a real-world application (although that's purely speculation on my part as I wasn't the one making the claim - but it's certainly a reasonable consideration).
Secondly, very few people actually recommend running T5HO actinic lamps. A typical application would include lamps measured some where around 450nm but generally not pure "actinic" 420nm. And as an example even a 250W AB 10,000K on an M80 ballast has its largest peak at 420nm (actinic) so I suppose it's producing false high PAR readings?