watts vs lumens?

[herbnjill]

I know there is a difference between watts and lumens. Watts being what you pay for (energy used) and lumens the amount of light actually put out. That brings me to the question of which lights are more efficient? Does anyone out there know which types of lights put out the most lumens per watt?

 

[thegrog]

You are kind of comparing apples to oranges here. A watt is a unit of energy (like you said, what you pay for in killowatt/hours......number of kW you use in an hour) but Lumens is a measurement of a bulbs brightness (the measurement of the amount of light produced). You can have a very high wattage bulb that produces very little lumens as you can have a low wattage bulb produce a lot of lumens.
Now, efficiency. Metal Halide bulbs are probably the most efficient bulbs/lights widely available. They produce lumens in the tens of thousands (some in the 10,000+ range) for a few hundred watts whereas an incadicent bulb (like in your reading light) is 100 watts and maybe a few hundred lumens.
The HQI MH bulbs produce more lumens than the standard mogul based bulbs as well.
The other bulb types (VHO, PC, T5) don't come close to the watt/lumen ratio that MH has.
Hope this helps.

 

[herbnjill]

Exactly what I was was wanting to know, thank you! In all the threads I viewed all i ever heard was "watts per gallon" and I knew bottom line watts was just what you were paying for and didn't tell me how much light I needed to provide. Any idea on how to figure how many lumens per gallon and what kelvin ratings I should look for?

 

[thegrog]

Don't worry about the lumens per gallon. Just be sure to get an aquarium grade bulb and you should be fine.
If you have MH alone, go with 13,000-20,000K bulbs. If you are combininb with VHO or PC actinics, you can go with 10,000K.
As far as how many watts/gal:
soft corals 1-4
Most anemones: 4-7
Carpet & giant anemones & stony corals: 7+
If you are using HQI bulbs, you can reduce these numbers by 1 to 1-1/2 as they put out more light than standard bulbs.
Hope this helps

 

[bang guy]

Lumens measure how bright an object looks to human eyes. It doesn't really have all that much to do with how much light is produced.
PAR is the amout of useful light produced. That's what you should search for.

 

[shouse]

YOu sure that T5 is that much different than MH lumens wise???
As what i researched they seemed pretty much the same.
I've been trying to figure out what is it about MH's that makes the corals grow so well? Is it the high lumens? Bang Guy u said something about PAR, can you inform us about what that is? People seem so fast to trash T5's but i'm not so sure they are getting the credit they deserve. what do you think bang? thanks

 

[bang guy]

From what I have researched, Normal Output Flourescent Lighting seems to put out the most light per watt followed by High Pressure Sodium.
On the Lumen vs PAR.
Lumens are defined as the brightness and weighs light in the 550 - 560 nm range higher than the other wavelengths. This is because our eyes see yellows better than colors at the ends of the visible spectrum.
This makes it a poor unit of measurement for reef aquariums because we tend to avoid the middle wavelengths.
PAR is Photosynthetically Active Radiation. This is a pretty good measure of how much useful light is actually being emitted across all of the visible wavelengths.

 

[bang guy]

Originally posted by Shouse
I've been trying to figure out what is it about MH's that makes the corals grow so well? Is it the high lumens?
MH are a point source light and as such the light is far more intense than flourescent lighting. Increased intensity means deeper penetration. The current theory is that the light can go deeper into the flesh of the corals and illuminate zooxanthellae better.

 

[acekjd83]

I had never heard it put quite that way before, but it makes sense. If you close your eyes, you can still see a MH glowing through your eyelids, but not so with a fluorescent... excellent point bang guy

 

[shouse]

interesting, thanks bang