For total lumens - do you add both lights?

13 years ago

Ok- so I've read through tons of posts to not ask a question someone else asked... BUT.

I am trying to determine if I have enough lumens with my first cheap grow light...

T12 - 40W - 48" bulbs

1 is 6500K Full Spectrum Daylight - ~2300 lumens

1 is 3000K (warm white I believe) - ~1800 lumens

Is this sufficient for typical vegetable seedlings?

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Comments (13)

clones2
Original Author
13 years ago
I guess I am asking if there is a total lumens number that most people shoot for, for this purpose. Thx.
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taz6122
13 years ago
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.
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The light meter we have is a "regular" light meter, not the one on our digital SLR Nikon although that light meter was very close to the same readings. I know zero about overdrive fluorescents, only the typical, buy at a big box store for $2 a bulb light bulb that runs 3000 lumens, when first lit. They decrease over a matter of time. I do grow orchids including the high light orchids requiring fc of 2,000-2500. These I grow under HPS lights on a moving track. I grow the lower light orchids under the regular fluorescents and keep them actually touching the lights, putting the higher light requirement plants in the middle and the lower light growers on the end. All of these do grow and bloom on schedule but previously, they have been housed outside in the summer months for maximum growth to endure the winter months of less light. Soon, the orchids will be housed in a greenhouse and I can worry about them but in a different way. You are correct shrubs, most orchids with a required 2000-2500 fc's, take sun until noon, then shade. Most orchids that do prosper under regular fluorescents are the dappled or shade loving plants. Brooke
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I went to a local lighting store (where I had previously bought fixtures) and got free help with the design. My kitchen is 9.5 x 13 approx., unlike yours I have cabs down both long sides ( one of those sides is shortened by the doorway to the basement steps) so my light is confined to a smaller footprint. I have 5 LED recess kits, 3 on one side with the main counter and sink, 2 on the basement entry side next to the frig and pantry; each 800 lumens I believe (maybe 900) = 3600-4000 lumens, and even dimmed to 75-80%, I have more than enough light for the counters with upper cabs without turning on the UCLs. I really feel that I didn't need all the undercabinet lights -- I rarely turn them on. I am a bit older and really appreciate good lighting -- I go into the kitchen when I need to see small print well. So it seems to me that for your space around 10,000-12,000 lumens would be a ballpark. I have no idea how the use of track lighting for some of that will effect the dispersal and effectiveness of the light, though.
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clones2
Original Author
13 years ago
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...
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taz6122
13 years ago
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.
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wordwiz
13 years ago
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
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clones2
Original Author
13 years ago
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.
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taz6122
13 years ago
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.
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wordwiz
13 years ago
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
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taz6122
13 years ago
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.
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wordwiz
13 years ago
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
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taz6122
13 years ago
Sounds good! I know my plants are doing good so far. Thanks Mike!
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veriria
13 years ago
I've seen this "overdriven" word a few times now, but I don't know what it means...? Thanks in advance for explaining :)
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taz6122
13 years ago
There are many threads on the subject that a simple search will bring up.

Here is a link that might be useful: Search results
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For total lumens - do you add both lights?

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For total lumens - do you add both lights?

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