Does combining lights = combining lumens?

[cork144]

It's not about merging, he has two separate light sources occupying the same physical space. They don't need to "merge" for the area to have the total amount their output.

Why would the space have fewer lumens than the output of the 2 light sources?

hell have 2 seperate ammounts of lumens, hitting at different places, this does not add to a total ammount of lumens. maybe to lumens used, but not the ammount there.

 

[67gto]

Hey SmokinSHO, a quick question. If you have temps. under control what advantage would going to lower wattage give you?

 

[etinarcadiaego]

Yah Cork144 you're wrong. Lumens ARE additive.

Sorry man.

And what does this mean "maybe to lumens used, but not the ammount there."

Lumens used?

 

[pinecone]

I'm not convinced by the information in wiki - not that it matters.

The thing that trips me up: If the lumens "stack", there is no difference between two 50k lumen sources and 1 100k lumen source. This means that the inverse square law would apply equivalently to both sources which doesn't seem right. In other words I'm not sure that 2 sources emitting 50k lumens each is really twice the visible light.

Pine

 

[SmokinSHO]

...

 

[etinarcadiaego]

@ Pinecone. Lumens don't measure things like intensity, or even distribution (I think lux takes distribution into account), etc. More than that even, as I'm not a light expert. That said there are def. differences between two 50k and 1 100k light source, intensity being one. But lumens, a measure of perceived light, are additive.

The question I asked earlier, is

"Why would the space have fewer lumens than the output of the 2 light sources? "

 

[etinarcadiaego]

The inverse square law would apply to each light source individually I would imagine. Point source vs multiple point source.

 

[Owl Mirror]

Wouldn't this simply be: more lights cover more square foot space?
Is a fluorescent ballast better if it contains 2 or 4 or 6 or 8 or 12 bulbs?
If you put two 12 bulb flouro's side by side, they would cover more square feet yet, does it increase the amount of lumen's on any given spot below them ?

 

[BLUNToPOTomuss]

Yah Cork144 you're wrong. Lumens ARE additive.

Sorry man.

And what does this mean "maybe to lumens used, but not the ammount there."

Lumens used?

Lumens are NOT additive. You are wrong etinarcadiaego.

If you have 2 bulbs that are rated differently say a 40k and a 30k lumen, You can not add the lumens because they are from seperatate sources.

You can say I have a 40k and a 30k but not an output of 70k...... A full lumen count comes from a SINGLE source.

When you have 2 sources with one higher than the other it drowns out a certain percentage of lumens from the lower producing bulb.

Watt are additive not lumens, thats why its easier for noobs to use watts when trying to calculate how much light to use.

 

[whodair]

im sure its been said before but you're all pretty smart for a bunch of potheads!!

 

[silent_lemon]

Lumens are NOT additive. You are wrong etinarcadiaego.

If you have 2 bulbs that are rated differently say a 40k and a 30k lumen, You can not add the lumens because they are from seperatate sources.

You can say I have a 40k and a 30k but not an output of 70k...... A full lumen count comes from a SINGLE source.

When you have 2 sources with one higher than the other it drowns out a certain percentage of lumens from the lower producing bulb.

Watt are additive not lumens, thats why its easier for noobs to use watts when trying to calculate how much light to use.

QFT this right here is corrrrrrrrrrrrrrect.

 

[etinarcadiaego]

Lumens are NOT additive. You are wrong etinarcadiaego.

If you have 2 bulbs that are rated differently say a 40k and a 30k lumen, You can not add the lumens because they are from seperatate sources.

You can say I have a 40k and a 30k but not an output of 70k...... A full lumen count comes from a SINGLE source.

When you have 2 sources with one higher than the other it drowns out a certain percentage of lumens from the lower producing bulb.

Watt are additive not lumens, thats why its easier for noobs to use watts when trying to calculate how much light to use.

Why are we assuming one is higher than the other? How does light drown out other light? DO you have a source here to cite?

My question, which I will restate for the 3rd time in this thread:

Why would the space have fewer lumens than the output of the 2 light sources?

What is a full lumen count? We're not talking about the number of lumens falling on a point source in a grow room, we're talking about the number of lumens landing on a canopy with a room. So if X lumens are emitted from the top of the room, they don't cancel each other, and they DO land on the canopy, as yes LUMENS ARE ADDITIVE.

lol

 

[dongle69]

Just did a quick test with my light meter.
I put the light meter at a center point below the 2 bulbs.
8 inches below the bulbs, the lights spaced 8 inches apart.
One t5 strip - 260 footcandles
After turning on the second - 500 footcandles

 

[etinarcadiaego]

Thanks man. Proof!

 

[bud toker]

doesn't light and sound behave the same ? would two people screaming at 100 decibels each = 200 decibels? I don't think so but I'm not certain.

 

[dongle69]

+10 decibels = twice the volume (perceived).

Doubling of the volume (loudness) should be felt by a level difference of 10 dB
Doubling the sound pressure (voltage) level corresponds to a measured level change of 6 dB.
Doubling of acoustic power (sound intensity) level corresponds to a measured level change of 3 dB.

 

[cashmunny]

I have a 150w HPS that puts out 16,000 lumens and a 250w HPS that puts out 27,500 lumens. If i use both lights in a cabinet do the lumens add up to 43,500 or am i mistaken about this.

Yes they add. Although since your reflectors can't occupy the same physical space, your total light may be a little more spread out than just running a single 400W bulb. The important number is actually lumens per square foot on the plants. To be precise its the photosynthetically active photons per second per unit area that is important, but lumens per square foot is a good proxy (kind of).

I believe high noon sun is 5000 lumens per square foot . IMHO much more than that may be beneficial but the rate of return will be diminishing. My reasoning is that since cannabis evolved for millions of years under the light of the sun the plant has been optimized for a certain maximum light level.

It also might be slightly more efficient to run a single 400W bulb and ballast, because then you won't be dealing with the resistive losses in TWO ballasts. It's not that significant though.

 

[mosess187]

the last four guys are totally right!....also there are more lumens in 1 400 watt than there are in 400 watts of CFL's...i'm not a genius or anything, and i dont mean to sound like an ass, but if you had 100 kids screaming at the same time, isnt it louder than 1 kid screaming at the same time?....same goes with lumens and watts....only thing is that you can get your CFL's way closer to your plants with minimal burning to the leaves if any, than you could with say an 400 watt hps or MH...maximizing the amount of lumens your plant can recieve in your space of growing!....hope this helps out!...good luck and Keep.It.Simple

 

[BLUNToPOTomuss]

here is a link explaining the difference beween foot-candle and lumen.

and an exerpt from the1st part of the link.....

Candelas are a measure of the amount of light generated at the source. Lumens quantify how much of that light flows away from the source in all directions.

---So this to me sounds like you only count what comes from the source. 1 bulb at a time.

Foot-candles and LUX indicate how well the surface area of an object, wall or floor is illuminated.

---So......... IMO Foot-candle power is what is really additive not lumens.

this is why I think we (both sides) are lookiing at it differently.


OH.... By the way!!! +rep for etinarcadiaego! for being a stand-up poster! You are doing things right my man!!!!!!

 

[dongle69]

A Lumen is equal to one footcandle falling on one square foot of area.
Lumens can be measured from a light reflector, which does not throw light in all directions.
I don't see why any measure of light would not be additive, at least to some extent.
My light meter doesn't seem to care.