The Planted Tank Forum banner
21 - 40 of 776 Posts

·
Registered
Joined
·
172 Posts
I have been wondering how much PAR a typical T12 light produces. Like most everyone else I have just assumed that watts per gallon was a way to guess the light from T12 bulbs, but there is no more reason to expect that to mean anything than there is to expect it to mean anything for other bulb types. So, I decided to do some testing.

I borrowed a new two bulb 48 inch T12 light fixture from one of our local aquatic plant club members, bought a new T12 bulb - a Phillips "Natural Sunshine", 40 watt 5000K, 92 CRI bulb at HD, borrowed our club PAR meter and took some readings.
So you put one bulb in a two-bulb fixture?

I have two-bulb T12 shop lights, and when I install only one bulb, it lights up very dimly until I pop in the other bulb. Did you ever install a second bulb to see if there was a change in brightness?

I wonder if this could have given you incorrect data...
 

·
Registered
Joined
·
21,012 Posts
Discussion Starter · #22 ·
So you put one bulb in a two-bulb fixture?

I have two-bulb T12 shop lights, and when I install only one bulb, it lights up very dimly until I pop in the other bulb. Did you ever install a second bulb to see if there was a change in brightness?

I wonder if this could have given you incorrect data...
I didn't try two bulbs because I didn't want to pay for two. But, the bulb lit up as brightly as I usually see, anything but dimly. I don't recall any previous magnetic ballasted T12 fixture I have used doing what you saw, but I don't rule it out. The fixture had two power cords, two switches, so I assumed it was intended to run one bulb alone if desired.
 

·
Registered
Joined
·
172 Posts
I didn't try two bulbs because I didn't want to pay for two. But, the bulb lit up as brightly as I usually see, anything but dimly. I don't recall any previous magnetic ballasted T12 fixture I have used doing what you saw, but I don't rule it out. The fixture had two power cords, two switches, so I assumed it was intended to run one bulb alone if desired.
Ah. OK. My fixture has only one power cord and no switches - it lights up when it's plugged in.

I have 4 T12 bulbs 20" above the substrate, with mylar film affixed behind the bulbs acting as crudely designed refelctors. Light output is up over the white reflectors, and heat build up under the canopy is down. The mylar is better, but I really don't know how much better.
 

·
Registered
Joined
·
3,401 Posts
So you put one bulb in a two-bulb fixture?

I have two-bulb T12 shop lights, and when I install only one bulb, it lights up very dimly until I pop in the other bulb. Did you ever install a second bulb to see if there was a change in brightness?

I wonder if this could have given you incorrect data...
That's been my experience too. I was wondering with the t12 was sooo much lower than the pc and t5.
 

·
Registered
Joined
·
21,012 Posts
Discussion Starter · #25 ·
I did some experimenting with mylar, aluminum foil, and ordinary white paint as reflectors. To my surprise, the mylar was the least effective, the aluminum foil the most effective, but just barely better than white paint. I didn't use any special white paint, just what I had in a spray can at the time. I believe if you take care to get an ultra white paint you will get better results with that than with aluminum foil, and certainly better than with mylar. The differences I found were around 15-20% from best to worst, so the light doesn't look much different, but a PAR meter shows the differences.
 

·
Registered
Joined
·
21,012 Posts
Discussion Starter · #26 · (Edited)
Today, I went back over the data I received from others about various types of bulbs and fixtures, and realized that I could characterize non-AHS PC lights as well as the AHS lights, and that I had one data point for a 150 watt HQI fixture. So, I added that to my chart of PAR vs distance, double checking how I derived that chart. It changed a little, on double checking, but not significantly. Of course the HQI line is just there for comparison, it isn't nearly good enough to use for selecting that type of fixture. The other lines should be good enough to get you into the low, medium or high light categories pretty reliably.


EDIT:
Another way to use this is to convert it into a simple table, that lets you select a lighting option based on tank height, how high you want the light to be above the top of that tank, and how much light you want. This assumes that multiple bulbs are mounted close together, reflectors are typical for that particular type of light. And, I left out the AH Supply light kits.
 

·
Registered
Joined
·
142 Posts
Great work Hoppy!

How would you compare a single 2X overdriven 32W T8 bulb with a single normal T5NO bulb using an icecap reflector?

I have read a lot about T8/T12 vs T5HO but found little info on overdriven T8 vs anything.
 

·
Registered
Joined
·
399 Posts
I have read a lot about T8/T12 vs T5HO but found little info on overdriven T8 vs anything.
ODNO T8 output increases over normal T8 (from GulfCoastAquarian's ODNO thread):


  • 2xODNO (2 power leads per bulb) - ~50% increase
  • 3xODNO (3 power leads per bulb) - ~75% increase
  • 4xODNO (4 power leads per bulb) - ~100% increase
 

·
Registered
Joined
·
142 Posts
So assuming 1 [email protected]" gives ~10par, 1 T8ODNO 2X would yield ~20par. If I also assume that 1 T5NO gives about half the par of T5HO, I would get [email protected]" for T5NO.

The T5NO would yield ~10par more over the T8ODNO, that's not a lot but it gets onto the low light range(barley) for 20" depth.

Does this sound right?
 

·
Registered
Joined
·
399 Posts
So assuming 1 [email protected]" gives ~10par, 1 T8ODNO 2X would yield ~20par. If I also assume that 1 T5NO gives about half the par of T5HO, I would get [email protected]" for T5NO.

The T5NO would yield ~10par more over the T8ODNO, that's not a lot but it gets onto the low light range(barley) for 20" depth.

Does this sound right?
If 1 [email protected]" is ~10par, 1 T8ODNO 2x would yield ~15par, 3x would yield ~17.5par, 4x would yield ~20par
 

·
Registered
Joined
·
199 Posts
What's the conversion factor from LUX to PAR? I understand it would't be exact because of what PAR and LUX are and that different bulbs perform differently throughout the spectrum. Still, it would be useful information to have a ball-park idea of how the two compare from an average bulb.
 

·
Registered
Joined
·
21,012 Posts
Discussion Starter · #34 ·
What's the conversion factor from LUX to PAR? I understand it would't be exact because of what PAR and LUX are and that different bulbs perform differently throughout the spectrum. Still, it would be useful information to have a ball-park idea of how the two compare from an average bulb.
I haven't tried to determine the answer to that. Most bulb manufacturers don't print the LUX @ X inches rating on their bulb packages, so I never felt it was an important thing to know. I do know that the conversion factor would be much different for a GE9325K bulb, a 6500K cool white bulb, a 10,000K bulb, etc. How much different I don't know either. Someone else can have the fun of figuring this out:smile:

T5NO lights are interesting. I read a few years ago that the efficiency for converting watts to light for a T5NO bulb is higher than for a T5HO bulb. And, I know that for any given length bulb, T5NO bulbs are a little more than half the wattage of T5HO bulbs. From that you could assume that a 2 bulb fixture with T5NO bulbs would produce about the same or a little more PAR than a one bulb T5HO fixture. Except, that few T5NO fixtures use reflectors that are nearly as good as typical T5HO fixtures. And, the reflector accounts for a big percentage of the efficiency of T5 bulbs. Until someone gets several PAR meter reading for a few different T5NO fixtures I don't know how we will ever know how to judge those fixtures.
 

·
Registered
Joined
·
659 Posts
tom and hoppy where do you think my 192w (2x96w) power compact bulbs stand in the line of par now that they are over 2-20H tanks with the lights beening 18-20 from the substrate, oh and I also have c02 now just need to get the bottle filled and recert.
 

·
Registered
Joined
·
142 Posts
T5NO lights are interesting. I read a few years ago that the efficiency for converting watts to light for a T5NO bulb is higher than for a T5HO bulb. And, I know that for any given length bulb, T5NO bulbs are a little more than half the wattage of T5HO bulbs. From that you could assume that a 2 bulb fixture with T5NO bulbs would produce about the same or a little more PAR than a one bulb T5HO fixture. Except, that few T5NO fixtures use reflectors that are nearly as good as typical T5HO fixtures. And, the reflector accounts for a big percentage of the efficiency of T5 bulbs. Until someone gets several PAR meter reading for a few different T5NO fixtures I don't know how we will ever know how to judge those fixtures.
As far as reflectors go, a single bulb icecap reflector is no different on a T5HO then a T5NO right? Any upgrading I do will be a retrofit into my hood rather then a T5NO fixture.
 

·
Registered
Joined
·
1,115 Posts
Looking at a Coralife T5NO 2 bulb fixture, it looks as if maybe a third of the light being produced by each bulb is making it into the tank. The reflector design is just that bad.

So, it would probably take 2-3 fixtures, of 2 bulbs each, to equal the light from a single T5HO with a quality reflector.
 

·
Registered
Joined
·
21,012 Posts
Discussion Starter · #38 ·
tom and hoppy where do you think my 192w (2x96w) power compact bulbs stand in the line of par now that they are over 2-20H tanks with the lights beening 18-20 from the substrate, oh and I also have c02 now just need to get the bottle filled and recert.
Those tanks are 24 inches long, right? And, they are end to end, or 48 inches total length? With a pair of 35 inch long lights sitting on the top of the tanks? Assuming that is all correct, the half of each tank directly under the pair of bulbs, which have to be close together, given the 12 inch depth of the tanks, would be about twice what one bulb would give.

The big unknown is whether these are like AH Supply light kits, or like Coralife light fixtures. If like AH Supply, the PAR would be around 100 micromols of PAR, but if like Coralife, it would be more like 40 micromols of PAR. At the end of each tank not directly under the bulbs, the intensity would be quite a bit less.
 

·
Registered
Joined
·
199 Posts
Anybody here feel like lending / renting me a PAR meter? If so I'll take readings of a 10,000k T5HO and a 6700k T5HO at various heights in both PAR and in LUX and post the results. (Such a simple thing but no one has done this yet.)
 
21 - 40 of 776 Posts
Top