Does combining lights = combining lumens?

[ColBatGuano]

I used to be a camera and video tech--the other people who care a great deal about such things. In fact, the film (still and motion) and video industries are probably the reason light meters exist at all. Most of the down-time on video and film sets is due to lighting issues, most of which have to do with properly setting light intensity and color temperature to a fixed point using multiple source lights. I can tell you that lumens are most certainly cumulative. Now, it is technically true that 5000 + 5000 from different sources, no matter how close together, will not necessarily equal 10000 at any given point, but some of them will combine to increase the intensity at any points in space they meet. Any light metering instrument will verify this.

Light and sound do NOT behave in the same way. For example, sound cannot travel in a vacuum, but light can with great ease.

 

[etinarcadiaego]

Light and sound do NOT behave in the same way.

Yep

 

[BLUNToPOTomuss]

I used to be a camera and video tech--the other people who care a great deal about such things. In fact, the film (still and motion) and video industries are probably the reason light meters exist at all. Most of the down-time on video and film sets is due to lighting issues, most of which have to do with properly setting light intensity and color temperature to a fixed point using multiple source lights. I can tell you that lumens are most certainly cumulative. Now, it is technically true that 5000 + 5000 from different sources, no matter how close together, will not necessarily equal 10000 at any given point, but some of them will combine to increase the intensity at any points in space they meet. Any light metering instrument will verify this.

Light and sound do NOT behave in the same way. For example, sound cannot travel in a vacuum, but light can with great ease.

good post!!

by this it sounds like we are all right and all wrong at the same time!!

have a good night all!

 

[ColBatGuano]

Lumens, by the way, are not a measurement of light emitted from a source. They are a sort-of metric conversion of foot candles (light per square meter for lux, per square foot for foot candles,) which measure the amount of light reaching a source (illuminance.) Candlepower, or candela, is the measurement of light emitted from a source (radiance.) It is lux x 12.57 (the interior surface area of a one-meter sphere.)

You can't change how much light comes out of your light bulb. If you want to increase illuminance at a point, you have to either move the light closer, or add more lights. Physics is simple on this: the farther away from a light source and object is, the less illumination you get on that object. This is why we keep lights close to plants.

 

[cork144]

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?

im not wrong lol... i started off on cfls, if anyone needs to understand lumens its the cfl growers.

compare 250w cfl to 250w hps, or match the lumens of a 250 hps with "added" lumens, see whar grows the hardest nugs.

 

[dongle69]

OK I just tried 2 small flashlights.
I focused the beams so they were directly (and only) on the light meter.
Measured one at a time, then together.
Flashlight #1 - 540
Flashlight #2 - 400
Both combined - 930

 

[overmind1632]

This has been dicussed before about a year or two ago, I remember reading it. From that topic, it was shown that lumens DO ADD.

I just googled this

A LUMEN is a unit of measurement of light. It measures light much the same way. Remember, a foot-candle is how bright the light is one foot away from the source. A lumen is a way of measuring how much light gets to what you want to light! A LUMEN is equal to one foot-candle falling on one square foot of area.

So, if we take your candle and ruler, lets place a book at the opposite end from the candle. We'd have a bit of a light up if we put the book right next to the candle, you know. If that book happens to be one foot by one foot, it's one square foot. Ok, got the math done there. Now, all the light falling on that book, one foot away from your candle equals both…….1 foot candle AND one LUMEN!

 

[overmind1632]

im not wrong lol... i started off on cfls, if anyone needs to understand lumens its the cfl growers.

compare 250w cfl to 250w hps, or match the lumens of a 250 hps with "added" lumens, see whar grows the hardest nugs.

Exactly, this is very important to CFL growers, which I was one also

Like my previous post said, Lumens do add up

 

[ColBatGuano]

"So, if we take your candle and ruler, lets place a book at the opposite end from the candle. We'd have a bit of a light up if we put the book right next to the candle, you know. If that book happens to be one foot by one foot, it's one square foot. Ok, got the math done there. Now, all the light falling on that book, one foot away from your candle equals both…….1 foot candle AND one LUMEN!"

Whoever wrote that is absolutely correct.

 

[cork144]

nvm re-researched and im a dick, im wong

 

[overmind1632]

and think about it guys.......if lumens didnt add up, how the hell could ppl b growing with CFLs that only produce 1.7k lumens per a bulb....

 

[dongle69]

Referring to the cork post, watts don't equal lumens.
You can't compare by wattage figures, you need some unit of light measurement.
Wattage will help in determining the efficiency of your lumens, though.

 

[ColBatGuano]

Watts don't equal lumens.
You can't compare by wattage figures, you need some unit of light measurement.
Wattage will help in determining the efficiency of your lumens, though.

It's not just that helps, it is exactly how you would determine efficiency.

 

[cashmunny]

I wonder what would happen if you flowered plants under red laser light? Since it's coherent radiation I bet the effect on the plant would be interesting if you could get enough wattage.

 

[ColBatGuano]

The color temperature of the laser would have to be correct for photosynthesis, but a laser is a light just like any other. If it doesn't bring heat with it, and you could spread (not split) the beam wide enough, there is no reason it wouldn't work, too.

It would be a silly experiment, though, as there is no practical use I can think of for a laser with a beam wide enough to grow a plant.

 

[ColBatGuano]

If you all want to understand how light works a bit better, I suggest googling "light theory" and start with the first link to Wikipedia.

The other day I corrected a gentleman who was making the very rookie mistake of confusing color temperature with pigment color. Blue light means something entirely different than the blue paint on a car.

Do any of you wonder why, when you take pictures of plants under your lights, that the whole image often comes out yellow? It is because your camera's color balance is not calibrated to the color temperature of the room. Many cameras have a color balancing capability. The way you correct the color balance is by telling your camera what the color white looks like under your lights. Do this by getting the whitest flat-white sheet of paper you can find. Attach it to a flat board of some sort and put it at a slight upward angle near where you're going to shoot. Fill your camera's entire viewfinder with the white paper, then activate the color balance function. The camera will now see that color temperature as white, and your images will no longer be yellow. It will enable you to take great pictures of your plants. Color balancing, by the way, is effective in all lighting situations to remedy off-balanced colors.

Ever see a picture of a film or television set, where there is an easel set-up with some sort of test-pattern, color chart, gradient, or a series of progressively smaller black and white lines sitting on it? All of these aid professional cameras to get a certain "look" by balancing color temperature.