Improved spectrum/greater brightness

Hey folks,


I'm doing my first grow using an HID lamp (400 watt HPS ballast), and am currently vegetating one plant that's about a foot high and starting 8 seedlings that are anywhere from 0-3" at the moment (they all fit in an area that's about 2X2 feet, but the closet is more like 2X6). I have a Growbright Metal Halide conversion bulb with a 6000K spectrum that puts out 38,000 lumens. I also have a nice HPS bulb that emits 55,000 lumens. Is the improved spectrum of the metal halide a big enough positive change to make up for the almost 30,000 lumens lost in the conversion? Maybe my plants would actually vegetate better under the HPS because it's so much brighter? Any experiences or thoughts you guys/gals could share with me would be really helpful. Thanks in advance!

Someone will correct me if I'm wrong, but I don't think it's a wider spectrum for the MH, as much as it is which part of the spectrum... ie, MH puts out a ton of blue light. Thus, great for veg. But a MH's red spectrum is limited... which isn't great when you need it, ie during flowering. That's when your hps comes in, as it's red and not blue.

If you do want to switch over to the hps for veg (I use hps for everything), I suggest running a couple supplemental cool blue FLs... but even then, I think you're better off with the MH and switching up for flowering.

Parallax said:

Someone will correct me if I'm wrong, but I don't think it's a wider spectrum for the MH, as much as it is which part of the spectrum... ie, MH puts out a ton of blue light. Thus, great for veg. But a MH's red spectrum is limited... which isn't great when you need it, ie during flowering. That's when your hps comes in, as it's red and not blue.

If you do want to switch over to the hps for veg (I use hps for everything), I suggest running a couple supplemental cool blue FLs... but even then, I think you're better off with the MH and switching up for flowering.

Click to expand...

Okay thanks. yeah I'm aware that the focus so to speak of the MH spectrum is more suited to vegetative growth, but I'm wondering if the additional lumens that I'd get with the HPS would outweigh the spectrum advantage of the MH. I mean if I had a 55,000 lumen metal halide and a 55,000 lumen HPS, obviously I'd use the MH for veg and the HPS for flower. But when the MH is so much less powerful (38,000), is it really giving me an advantage during veg? Thanks again for the response, just thought I'd clarify...

Lumens is an antiquated way of comparing grow lamps. Lumens are a scientific definition based on the human eye and NOT on a plants response curve. It's just marketing hype to make you feel that one product is better then another. TO increase lumens most companies just bump up the parts of the spectrum that are the cheapest and easiest to manipulate. It just so happens that these parts of the spectrums are the least valuable to a growing plant.

Lumens are garbage and are nothing more then a tool to compare lights based off of the same technology with roughly the same light spectrum output. Nothing more.

they need and use more red light in flowering apparently,im no botanist,and they like lots of UV,Blue and iffy blue light in Veg