# Lumens and tube flouros



## booradley (Jul 8, 2007)

I have some t-5 2' fixtures. One is rated at 8000 lumens. Now, since they are 2 foot long tubes does that mean that every plant under that light (which is within 1-3" of my plants, is getting showered with 8000 lumens? Since it covers an area roughtly 2'x1' does that mean that it is basically 8k lumens per square foot? Or does that simply mean that the 8000 lumens is spread over the entire distance the lamp covers? I understand CFLs and HIDs where the light more or less originates from a single spot and all the light is spread out from there. The plants closest to the ligths are going to get hit with the fullest force of the light. Is the same true with tubes? Or is the light just more defused? 

So if I had 1 cfl with 8k lumens and a my t-5 with 8k lumens in the same sized space (1.5'x2') would the growth rate be more or less the same? Providing everything else was the same that is...

Sorry if this is a really simple and stupid question that has been asked a million times, but I did browse the stickies before asking.


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## Dankerz (Jul 8, 2007)

t-5,2' 4' etc carries the lumens threw out the whole bulb. the cfl would have the same lumens but the lumens would be condensed being they are more compact rather than spread out.
if your growing alot of plants its better to have a lamp that is spread out so you can get more under the lamp rather than sqweezing them all under a cfl


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## booradley (Jul 8, 2007)

So in basically 1 8000 lumen CFL with three plants: one directly (3 inches) under gets 8000 and two off to the side get 5000. That I get...  

But with 8000 lumens of t-5 tubes do the 3 plants 3 inches under get 8000 lumens or does the tube disperse the lumens along the length of the bulb so you're only getting about 6000 lumens per plant?

BTW, those numbers are being pulled outa my... well, they're there simply to demonstrate my query and not to represent actual numbers.


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## Dankerz (Jul 8, 2007)

:--------------------: <t5bulb
^^^^^8000^^^^^

8000 the whole length

even know i dont think they are 8000


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## booradley (Jul 8, 2007)

Dankerz said:
			
		

> :--------------------: <t5bulb
> ^^^^^8000^^^^^
> 
> 8000 the whole length
> ...


 
I get it. I am thinking in terms of the entire fixture giving off 8k lumens. Since there are four bulbs it is this:
]:--------------------: <t5bulb
^^^^^2000^^^^^

Whereas a 2000 lumen CFL would be:
:----:
2000      1000      500

or somesuch.


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## anonymous (Jul 9, 2007)

As far as I know that's incorrect.  The TOTAL output of a bulb all together is it's lumen output.  Therefore each point on the tube would not be putting out 8k lumens, as you guys seem to think (if I'm understanding you).

BUT, if you have the plants spread out, the tube is still better... and here is why.  With the tube, each plant is getting the same amount of lumens... whereas with a CFL, the one in the middle is getting the most, then the plants as you move farther away from the bulb are getting less... which is not ideal.  Obviously since the tube light is the same distance from each plant, they're all happy and sharing.

You have to keep in mind the sq. footage of the grow space.

Here is how it works in pic form (estimated) using 4 plants.

8000 lumen, 2ft long... so obviously covering 2 sq feet of grow area...

:=================: <- long tube bulb.. ==== is the actual tube (ignore the dots and lines here... had to use because spaces go away on this forum)
---\/---\/---\/---\/ ---
---2k---2k--2k---2k

See that would give you a total of 8k lumens, but an even 2k lumens per every 6 sq. inches.  Also consider that light is wasted that goes up and to the sides but for both of these drawings we're considering perfect conditions (no light is lost) and the use of a reflector, etc.

Now... a CFL would be more like this.

8000 lumen CFL (so total amount of light is same), same 2 sq. ft. grow area, same amount of plants.

.............(=).............  <--- crappy drawing of CFL.. (=) is the bulb. (ignore the dots and lines here... had to use because spaces go away on this forum)
---/----|----|----\---
--1k---3k---3k---1k--

Again those numbers are rough estimates but the point stands.  Note I tried to use the same amount of space even on this post for both types of light to represent 2 sq. ft of space for both.  The only problem is that the forum took out all my spaces in between the lines, slashes, and "plants" so you will have to use your imagination.  The 1k, 5k, 5k, etc. represent plants and how many lumens they're getting.


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## booradley (Jul 9, 2007)

Well, that's my question, isn't it? Which way is correct? Anyone have a definative answer to that?


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