lightgin

[Hans]

i am just curious, why does everyone use watts as a system of light measurement? why not lumens??

its like in audio, some speakers are rated at 200 watts, because it TAKES that much power just to make them play. some would play insanely loud an blow up wiht 200 watts going to them. thats why sound is measured in decibles, watts has always been a marketing strategy, buy this neon its got a 200 watt stereo!

you would think, people as smart as fishkeeprs would be using lumens per gallon, and then add or subtract depending on tank height??

[Hound]

If I'm remembering correctly lumens measures what we see and not what plants or fish need or require. That is you can take a 2500k soft white light with a high lumens rating and put it over your planted aquarium, but you would do better with a 6500k bulb with a lower lumens rating.

[Hans]

so how do you measure plant loving brightness?

[happychem]

If I recall correctly, speaker wattage refers to how loud they can go, assuming you put in the enough power.

The colour temperature is a pretty good approximation. Generally about what 6500K for FW plants? Lumens isn't a bad idea, except that they're non-specific units. Except that when Lumens are listed for a bulb they refer to the amount of light emitted as the human eye picks it up. Now if one were to specify x Lumens at 380nm, then we'd be talking. But evolution set us up to see greens better than reds and blues, so nuts.

The same problem with CRI, it refers to how natural the light looks to us.

Hence watts. You assume a decent reflector and the correct colour temperature, then watts are the power of the light, more or less.

But why ask this Hans? I've seen pics of your tanks, you seem to have things under control...

[TonyN]

Actually, the wattage rating on a pair of speakers refers to the amount of power they can handle before blowing up.

[Richer]

I agree, watts is inaccurate when it comes to providing light... whether for plants, or corals, etc. 175 watts of incadescent lighting cannot compared with 175 watts of CF lighting... nor can 175 watts of CF lighting compared with 175 watts of MH lighting. However, I believe we use watts/gallon not as a definant measurement, but as a general rule of thumb. Though not a completely accurate general rule of thumb, its still useful.

Other things can also come in to make things more complicated. Like what kind of reflector is being used. I can get a 36 watt CF light fixture outperform a 55 watt CF light fixture if I wanted to. I'd just put the 55 watt on with no reflector, and give the 36 watt a top of the line reflector. Where the light is focused is also another issue. MH lighting, though efficient and powerful, only focuses its light on a certain area, whereas CF bulbs, or flourescent bulbs spread their light over a larger area.

BTW, the general lighting rule of thumb in planted aquaria tends to refer to using normal output flourescent lighting. Adjust the amount of watts you use according to what kind of light you plan on using... (ie. you can get away with a little bit less wattage using a power compact system).

HTH
-Richer

[Hans]

Originally posted by TonyN
Actually, the wattage rating on a pair of speakers refers to the amount of power they can handle before blowing up.

thats what i said??