The new T5 and T8 fluorescents have higher light output (3400 and 5000 lumens) than the conventional 48 inch T12 (1700 lumens).
Has anyone used the new lamps to grow seedlings indoors, and have you noticed an improvement in seedling growth?
Not all T12 fluorescent lamps have the same output. The T12 is available in both 34W and 40W. The 1700 lumens is pretty close to the bottom end, as I recall, and probably corresponds to the 34W T12. The output of the Cool White Deluxe 40W T12 (Sylvania CWX, for example) is down in the 2200 lumens range, but the standard 40W Cool White produces quite a lot more, in the 3000 lumens range. Right now I am running some 40W T12 Cool White Plus tubes from Sylvania, and they’re rated at 3000 lumens.
I’m not sure how the T5 and T8 tubes fit in here, but I’m guessing the cost/output ratio of the T12s will be hard to beat.
Take a look at some of the comparisons at the link below.
Peter
Actually, I switched over to all T8 light fixtures about 2 years ago. My goal was to become more energy efficient (T8s are more energy efficient than T12, using less wattage to produce equivalent or higher intensity lighting). T8s have a very wide range of bulbs to select from. I typically order in bulk from 1000bulbs.com. I tried a couple of different Kelvin spectrums but have now settled on using the F32T8 5000K Hi-def full spectrum bulbs. These are 32W bulbs that produce about 3050 initial lumens. I have excellent growth rate results with these lights and they are ironically cheaper than some other bulbs I tried earlier on that did not provide nearly the results I get now. I can’t remember exactly what Kelvin range I tried one time…but it was horrible and the foliage on the leaves looked very chlorotic and blotchy. At the time I knew it had to be the lights because I had changed nothing else about the growing environment and soil. Needless to say, I quickly switched to other bulbs.
Peter, I think you actually posted a link to that site a few years ago, as I distinctly remember referencing some of that information when I was trying to work through all of the different Kelvin, CRI, and lumens ratings. Very helpful information.