watts VS. lumens

[RTR]

Minor clarifacation - K or Kelvin ratings cannot be arbitrary, they are measured quantities and misstating them could constitute fraud. But they do not necessarily predict what the visual or plant growth effect will be. It is a measured reading of the total effect of the bulb/tube, while visual impression and growth effect both depend on the particular spikes of the three phosphpors used.

But I agree that ~6700K tubes tend to be pleasing to many folks, including me. The majority of my lights are 6500-6700K.

 

[Slappy*McFish]

Some bulbs I've had the best luck growing plants with include:
- Zoo Med Ultra sun 6500K
- Coralife Trichromatic Super Daylights 6500K
- Triton
- GE Freshwater/Saltwater 9325K

 

[H3D]

No, more lumens only mean that more of the output is in the range where the human eye is most sentitive, not necessarily in the areas which plants use, or which will give the best cotor redition for us.

Not true...lumens measure the total amount of all light given off buy a light source. The Kelvin range of the bulb is what determines the color of the light given off.

 

[phanmc]

Not true...lumens measure the total amount of all light given off buy a light source. The Kelvin range of the bulb is what determines the color of the light given off.

Incorrect, lumens is the measurement of light energy perceived by the human eye and not the entire radiation range. Lumens doesn't account for UV radiation for example. The photosynthesis process of plants uses a wider range of radiation energy than the human eye and has a separate energy rating system called Photosynthetic Active Radiation (PAR).

Specialized plant bulbs that emits the pinkish or purplish light have less lumens (appear dimmer) than full spectrum lights but their PAR is equal to or higher.

 

[H3D]

Incorrect, lumens is the measurement of light energy perceived by the human eye and not the entire radiation range. Lumens doesn't account for UV radiation for example. The photosynthesis process of plants uses a wider range of radiation energy than the human eye and has a separate energy rating system called Photosynthetic Active Radiation (PAR).

Lumens (the amount of light given off) are measured by photons hitting the surface of a photodetector...which has nothing to do with human visability. PAR is measured by the numer of photons within a specific light waveband (400-700nm). When lumens are measured the light in this spectrum is measured as well.

Specialized plant bulbs that emits the pinkish or purplish light have less lumens (appear dimmer) than full spectrum lights but their PAR is equal to or higher.

These bulbs emit the same PAR because both have the same amount of light in these wavelengths(400-700nm)...the reasone their lumens are less is because they do not emit the other parts of the light spectrem...and are therefore less bright.

 

[RTR]

Don't squabble. Look it up. Lumens are defined by human perception, not by total light emission.

Strat with: http://www.thekrib.com/Plants/Tech/intensorama.html

Then go to more technical sources.

 

[H3D]

Don't squabble. Look it up. Lumens are defined by human perception, not by total light emission.

Strat with: http://www.thekrib.com/Plants/Tech/intensorama.html

Then go to more technical sources.

This is a technical source? This is a direct quote from Stephen Pushak's article:"This gives me enough data for some serious scientific wild a** guessing." His article is based on the information from the Wright Huntley's article in which he bases his data on techniques that were used 60 years ago...before photons were reliably detectable. This info is as out of date as AC's fish profiles(most of them are over 100 years old).

For real technical source about light visit:http://www.cbpf.br/pdf/Light Measurement Handbook.pdf

Compare Wright Huntley's chart of what light is visible to a human eye to Alex Ryer's, a real scientist. Huntley's chart is missing a large portion of what we can see. Huntley's article also fails to distinguish between "visible" light and what the human eye can see. A human eye can see most of the light that falls in to the PAR category, and all PAR light falls in the "visible" light spectrum(380-770nm). When a photometer measures light it measures this entire spectrem of light.

Here is an article about how a photometer works:http://www.fiberoptix.com/technical/measuring-intensity.html

While a photometric measurement such as lumens gives weight to the sensitivity of a human eye, because we cannot see all UV and IR light in the spectrum, it still measures all light in this spectrum. A PAR measurement is only slightly more accurate because no weight is given, however since most PAR light is visible to the human eye it is detected in a photometric test.

 

[RTR]

I did not say that The Krib was a technical source, did I? I said that it was place to start. And that it could be followed by technical sources. Do not put words into my mouth that I did not say.

 

[H3D]

Sorry. I was not trying to put words in you mouth...I just like to joke around. :joke: When you said:

Then go to more technical sources.

The word "more" implies that the fist was technical. I was only making a joke cause I thought it was funny. :laugh: But apparently you did not think it was. :rant2:

 

[Bigbob55]

Hey guys, I'm a physics major.

The formal definition of a Candela (lumen = candela / m^2) is the amount of radiation of light given off by a source when illuminated by light of frequency 540 X 10^-12 htz (wavelength = 550 nm) at a power of 1/683 watts.

So the Lumen measures the amount of light energy given off at a certain frequency - which happens to be the middle of our visible spectrum, and the color we are most sensitive to, yellow-green.

If lumens were measured by detecting photons, then you are really measuring watts. And lumens would just be watts times a defined constant, which is why the specific frequency is used - to seperate it from the watts unit, otherwise the lumen unit is pointless.