I'm going to be ordering some more T5s soon. I've been using them as side lighting, but I think I'll be starting an all T5 grow soon.
In light of all the problems with Red Suns, I may try some of the Philips red bulbs I posted graphs for a little while ago. If so, I'll let y'all know how they compare!
Also, I've been thinking about something that I think could use some clearing up. As PAR/PUR-educated growers, we don't worry too much about lumens. But why?
A 1000w HPS puts out about 150k lumens (I'm looking at an AgroMax bulb at HTG supply for that number), a 600w HPS puts out about 95k lumens. A 400w HPS is rated at 55k. Meanwhile those 8-bulb New Wave T-5 fixtures mentioned recently are rated at 40k lumens. So with two 600w HPS bulbs you get 190k lumens, where as with the same wattage of T5 panels you only get 120k. Given the significant decrease in lumen output, how can we expect the T5s to compare to HPS, even with more PAR?
It has to do with how lumens are measured.
I'm no expert on this, and would love confirmation from someone who is or an awesome link or something like that, but my understanding is that lumens as a measurement are "calibrated" for the human eye.
Because the human eye sees green/yellow light more intensely than red/blue, a certain amount of green light will produce (a lot) more lumens than the same amount of red light. As a result, these color lights appear less bright to us, but not to plants, which as we know are much more interested in red/blue light.
Why does this matter to us? Because we look at some of these base bulbs and they look pretty darn white to us. But, maybe they should, right? Even though there may not be as much yellow/green light as red/blue light in these bulbs as many of the graphs show, they should still appear whiter to us than we might expect, because the green and yellow that is in the lights
will appear brighter to us than the red/blue light. (I'm talking about base bulbs - Fijis and their alternatives, not actinics, Red Suns, etc.)
In fact, according to this graph, the human eye uses light essentially opposite from photosynthesis in terms of efficiency, so clearly our eye is not a good judge of spectrum/light intensity for this application.
View attachment 1948153
Source:
The Perceptive Efficiency of the Human Eye as a Function of Wavelength
Thoughts? I wish I had a better source for this information.