PAR 38 LED PAR Readings

[zygote2k]

I tested my 4) P38 LED's today with the Par meter.

 

@bulb white 2000+

@bulb blue 2000+

 

1" below white 2000

1" below blue 1000

 

6" below white 1500

6" below blue 500

 

1" below surface white 1000

1" below surface blue 200

 

6" below surface white 750

6" below surface blue 100

 

12" below surface white 500

12" below surface blue 25

 

24" below surface blue and white 75

 

Ecoxotic 453 Panorama strip

 

At bulb 1200

1" below 600

6" below 50

1" below water 10

12" below water 5

24" below water 1

 

Since I have 40 degree optics, the values can change drastically if the meter is outside the cone of light. For instance, @ 6" below the bulb, between the 4 individual bulbs, the meter reads 200. One of the bulbs is a 60 degree and I cannot notice a difference between the 40's and the 60's. Remember, these are spotlights and coral placement needs to be thought out carefully when using them.

My acros are up high, LPS medium, shrooms, zoas, montis from low to bottom of tank. I have several corals directly on the bottom in the 20-50 zone and appear to be doing fine. The big derasa clam is in this low par zone and opens fully.

If I base the corals appearance vs. the par readings, then I can only assume that what we know about PAR and coral growth must be different when using LED's.

[jason the filter freak]

Any shots of the light in action?

[trockafella]

Now we need numbers for the 60degree optics, any chance you can get those..?

[gmubeach]

I have 60degree optics and what not just not sure how to determine par... anyway if you want to see pictures go to me tank forum... If someone wants to show me how they are welcome to!

[zygote2k]

Now we need numbers for the 60degree optics, any chance you can get those..?

One of the 4 bulbs is a 60 degree. I noticed very little difference in the PAR readings between 40's and the 60.

[Coral Hind]

One of the 4 bulbs is a 60 degree. I noticed very little difference in the PAR readings between 40's and the 60.

 

That is good news. Is there a noticable difference in the light spread?

[trockafella]

Ive seen the 40 and 60 optics together and you can see a difference.. I also dont think the 40 optic spotlight is as dramtic in a tall tank, it has more room to expand.. Those numbers are pretty good though.. After last months energy bill I am really leaning towards LEDs.. I dont care if the bulbs only last 3 years, going from 700+ watts to 150 watts and no chiller and less ac, I think I can justify the purchase.. Though im not sold on PAR 38's, I am sold on LEDs.. Sorry Rob, you got me half way there, just thinkin about going a different route.. Thanks for the post though.. Proof is a good selling point...!!

[JpNuss]

I understand being for LED's for the reasons of heat output, power usage, bulb temperature, etc. etc. But, does the intensity of the LED light truly compare to the intensity of halides or T-5's? I'm too new to this hobby and I'm having trouble fully understanding this question. Ps: Does this fixture need no hood for directing light?

 

All of these questions may seem novice, but I'm a physicist first and a hobbyist second!

[ctenophore]

I understand being for LED's for the reasons of heat output, power usage, bulb temperature, etc. etc. But, does the intensity of the LED light truly compare to the intensity of halides or T-5's? I'm too new to this hobby and I'm having trouble fully understanding this question. Ps: Does this fixture need no hood for directing light?

 

All of these questions may seem novice, but I'm a physicist first and a hobbyist second!

Yes, the intensity is comparable to metal halides and exceeds T5. However, the LED PAR38 bulbs do not put out as much light as an average 175w metal halide bulb. What they do put out is highly focused and intense. IIRC, the 3w LEDs used in the PAR38 bulbs are capable of about 150 lumens/watt, which is more efficient than the average MH bulb's 100-120 lumens/watt. But since the PAR38 is only 21w total, you're getting roughly 3150 lumens/bulb, all directed downward in a 40deg. cone. No reflectors are needed since the LED emits light in a single direction. Compare this to a 175w MH @ 110 lumens/watt = 19250 lumens/bulb, which is emitted in 360 degrees, hence the need for a good reflector. Much of this light is still wasted by spillage due to reflector inefficiency.

 

If you hold a PAR meter close to both LEDs and MH bulbs, you will max out the meter. Intensity falloff still follows the inverse square law though.

[zygote2k]

I tested a 6 bulb 60 degree tank today. rough numbers 600 near the surface, 300 8" down, 50 on the bottom. This is a shroom tank so 40's aren't needed. Remember, it only takes a few minutes to change a lense. Technically, you could use 1 bulb and put a variety of different lenses on each emitter and it might give you wildly different effects. Options for these bulbs are red, white, blue and 40, 60, 80, 120 degree lenses.

Maybe my next batch of bulbs will be 2) whites with 40d, and 3) blue- the 2 outer ones with 120d and the center with an 80d.

I think if I had $3k to spend on a custom light set, I could make a true dawn to dusk effect with 24 bulbs and a light controller- this would look like a Pink Floyd stage rig...

[JpNuss]

Yes, the intensity is comparable to metal halides and exceeds T5. However, the LED PAR38 bulbs do not put out as much light as an average 175w metal halide bulb. What they do put out is highly focused and intense. IIRC, the 3w LEDs used in the PAR38 bulbs are capable of about 150 lumens/watt, which is more efficient than the average MH bulb's 100-120 lumens/watt. But since the PAR38 is only 21w total, you're getting roughly 3150 lumens/bulb, all directed downward in a 40deg. cone. No reflectors are needed since the LED emits light in a single direction. Compare this to a 175w MH @ 110 lumens/watt = 19250 lumens/bulb, which is emitted in 360 degrees, hence the need for a good reflector. Much of this light is still wasted by spillage due to reflector inefficiency.

 

If you hold a PAR meter close to both LEDs and MH bulbs, you will max out the meter. Intensity falloff still follows the inverse square law though.

 

That's absolutely great information. Thanks a lot.

[thewire]

What kind of PAR meter you are using? I read somewhere that Apogee meter give false reading on LED especially the blue.

 

 

The biggest problem with the Apogee meter is its response curve in the 350-500nm range. At about 420nm, its only counting 50-60% of the photons.

 

This was troubling to me when we ran our own analysis with the Apogee QMSS, since I was getting higher par readings with PCs watt per watt than some of our HQI systems. And the results were even more dramatic when we put in 2 PCS of DAYLIGHT color (vs 2 x 5050s).