Lights online

[Merlyn]

Well, the watts/lumens DOES vary with the length of the tubes. So you might have the same color but not the same light output. INOW, you might grow Catts under a 4 foot T5 but you won't under a 2 foot because approximately 1/2 the lumens is not enough for them (just a hypothetical example).

[camille1585]

I never said that watts/lumens don't vary with the length of the tube, but that color K is something entirely different that has nothing to do with tube length! I was correcting only the second part of your comment: "4100k might be as high as 2 foot bulbs go"

[Merlyn]

I know, just making it clear.

[johnblagg]

Hmmm since ouput is measured in lumens per watt not lumens per foot something there doesn't sound quite right. A 4 foot tube will indeed produce more lumens but it will be equally distributed along the 4 foot and the wattage is what determins the total output so if you have a 2 foot tube that is 28 watts and a 4 foot tube that is 56 watts you get the same lumens per foot basicly so in fact you could grow the same plant under either tube ....You just dont have room for as many plants. 28 watt 2 foot t5s = 2800 lumens I think where as a t5ho bulb 54 watts 4 foot long puts out 5000 lumens ....so actually the 28 watt 2 foot tube is actually more efficient and giving more lumens per tube in a smaller area

[Merlyn]

Sorry, but your "Lumens per watt" is an efficiency rating. Lumens IS the variable output and is not determined by wattage which is a constant. I just walked into my plant room and on 2 different boxes of T8s the lumens were rated as 2750 and 2950 and I know there are tubes with much higher lumens. The T8 wattage in a 4 foot bulb NEVER varies and is ALWAYS 32 watts ! I think the lumens are varied by the type of gas and the inner coating of the bulbs.

[bballr4567]

Good info for sure now. Lol

[johnblagg]

Lumens are not directly proportional to wattage ? in that case lumens would have absolutly nothing to do with efficiency.....yes it is a measure of efficiency meaning you do in fact get more lumens per watt of power input. A 32 watt tube can in fact be over driven with electronic ballasts to put out more light and be ran at higher wattage than the bulb says it is made to run at and the gas type and phospors are not changed the only thing changing is the wattage you are pumping into it and in return you get more lumens out .....

[Merlyn]

Not to get technical or anything but WATTS is the output measured in heat and/or light, NOT the input. VOLTS is the input. No, they're not DIRECTLY proportional. How else do you explain GroLux vs. Cool White vs. Soft White, ALL of which have different lumen ratings ? Yes, you can over amp ONLY because there is a ballast that can be varied between the voltage and the watt output. That's a sidetrack from the original question, lumens are not DIRECTLY proportional to the watts or you're going to have a hard time explaining the difference in the SAME ballast with different type bulbs that are rated with DIFFERENT lumens. I'm waiting to hear this !

[johnblagg]

The watt ( /ˈwɒt/ wot; symbol: W) is a derived unit of power in the International System of Units (SI), named after the Scottish engineer James Watt (1736–1819). The unit, defined as one joule per second, measures the rate of energy conversion......

different bulb different gas ect as you so aptly pointed out....everthing else being the same aka same bulb then more watts = more energy converted thus more light. More light more lumens per watt.

[Merlyn]

That's ok, you're right and I'm right also. I get your point, but you missed mine. BTW, I guess you don't worry about cost efficiency because if you overamp your bulbs they fade out quicker = UNefficient cost wise and I'll not argue that point with you.