I guess I am asking if there is a total lumens number that most people shoot for, for this purpose. Thx.

Why mix bulbs? 2 6500k bulbs would give you 4600 lumen instead of the 4100 you're getting. More light = shorter, stockier and stronger plants. The slight difference in color temp will not make any noticeable difference in quality. I use 4 overdriven bulbs on each shelf. My lights put out close to 5000 lumen each for a total of around 20,000 per shelf but I can grow plants that set fruit inside. Your setup will work for seedlings but they will get a little leggy.

The warm white is actually 3300 lumens...

So my warm white at 3000K is 3300 lumens... but the 6500K is 1000 lumens less.

Doesn't make total sense to me...

AFAIK there's no T12 that puts out 3300 lumen and if there was it wouldn't be 3000k. I'm sure you are mistaken.

Lumens are not as important to plant growth as FootCandles or Lux. Lumems measure the amount of light coming from a bulb - FC/Lux measure how much is hitting a square foot or square meter. 4100 total lumens over four square feet is not much light - that why most growers use two sets of lights per a 1x4' shelf and move them much closer to the plants - it increase the intensity (thus the FC/Lux) of the light.

Mike

FYI for taz...

http://ecom.mysylvania.com/sylvaniab2b/b2b/start.do?browsername=mozilla%2F5.0%2520%2528windows%253B%2520u%253B%2520windows%2520nt%25205.1%253B%2520en-us%253B%2520rv%253A1.9.2.16%2529%2520gecko%2F20110319%2520firefox%2F3.6.16&browsermajor=5&browserminor=5

Not sure if this is the exact one I have... but it states Color Temp 3000K - Initial Lumens 3300

Thanks for the help - we can consider this closed.

Please give us an address we can use!

Mike since bulbs don't list the FC/lux the only thing we have to go on is lumen and color temp. I'm not into buying a light meter, then buying every type of bulb to measure the FC to determine which one is best.
So far IME anything between 4100k and 6500k is best. Any lower is too red and any higher is too blue.

taz,

Generally, lumens = FootCandles at a distance of one foot away.

One of the first tools I bought after I started growing plants was a light meter. Not an expensive one, but it does the job. I don't need to guess if the seedlings are getting enough light.

Mike

So if I'm running 20,000 lumen at one foot then at 1-2" am I doubling that +/-? Too early for me to do math, lol. I had a light meter when I originally set the overdriven lights up but just measured at a foot away and I am getting +/- 10,000 from each fixture.

taz,

According to the inverse square light, if the distance is cut in half, the intensity is going to be four times greater. At six inches, you should get about 80,000 lumens. But this is for a light is a point source. With a tube light, the measurements are different. In my measurements using fluros as well as MH, I find that cutting the distance in half roughly doubles the intensity.

Mike

Sounds good! I know my plants are doing good so far. Thanks Mike!

I've seen this "overdriven" word a few times now, but I don't know what it means...? Thanks in advance for explaining :)

There are many threads on the subject that a simple search will bring up.

Here is a link that might be useful: Search results