Success with LED and SPS

[sphelps]

Originally Posted by kien

I think they could do this today. Create a unit with an LED pod distribution like the GHL Mitras with each pod housing a tightly packed LED array like the Kessil.

That will be the killer LED light. Unfortunately it is probably cost prohibitive today

While in theory that makes sense in reality it's not necessarily true. The kessil doesn't have the same amount of colors in the GHL so while you may think the kessil is better at color blending it's not really the same. While the pods in the GHL may look pretty basic apparently they were designed specifically for maximum color blending and efficiency.

Light distribution

A homogeneous illumination is as important as a high light performance. Our engineers determined the best possible arrangement of the LEDs and design of the reflectors through extensive computer simulations and practice tests. With the goal to achieve an optimized illumination the LEDs have been arranged in 2 x 3 evenly spread clusters and all LEDs in one cluster are placed with a minimal clearance to each other. Additionally the clusters had been brought to the edge of the lamp as near as possible. The results are convincing:

Ideal mixing of the single LED-colors, the light in the aquarium has no disturbing color spots
Uniform illumination over a wide area
Efficient heat dissipation over the heat sink

Also consider the spread, the kessil is pretty tight which probably aids in the blending, if you widen the optic to be more comparable to other fixtures you may lose what you've gained. The Kessil is just a multichip LED which may or may not be the way the industry will go, in the end you're still looking at different colored light sources, packing them closer together may not make a difference and only cost you more in efficiency. Cost wise multichips are available and realistically cheaper than multiple single LEDs in terms of watts/$.

[kien]

Originally Posted by sphelps

While in theory that makes sense in reality it's not necessarily true. The kessil doesn't have the same amount of colors in the GHL so while you may think the kessil is better at color blending it's not really the same. While the pods in the GHL may look pretty basic apparently they were designed specifically for maximum color blending and efficiency.

ya I wonder what a kessil would look like with more colours. That would be interesting for sure. Honestly I don't quite understand why there is a red channel ? Is it just to add that particular spectrum? I found (to my eyes) that the addition of the red and green channel made the light look worse and I had to turn them both OFF to make the light pleasing.

[sphelps]

Originally Posted by kien

ya I wonder what a kessil would look like with more colours. That would be interesting for sure. Honestly I don't quite understand why there is a red channel ? Is it just to add that particular spectrum? I found (to my eyes) that the addition of the red and green channel made the light look worse and I had to turn them both OFF to make the light pleasing.

I think you really need to spend more time with the LEDs on your hands. I know when I first experimented with them I hated everything about them. After playing around with them they grew on me very quickly. Red and green are key addition IMO and most others who have compared with and without will agree, you only need very little but I found it applies less demand on the white LEDs creating an RGB effect which prevents many colors from being washed out. LEDs are different from T5s and Halides, realistically they shouldn't be compared too closely. If you switched from all halides to all T5s or vise versa you would have much to say as well. That's why MH & T5 combinations exist and are so popular but personally I think the T5 and LED combination idea goes against the main goals from LEDs in the first place.

[chatyak]

I haven't read the entire thread - but do you have a PAR meter? Especially if the colors are in the blues on the LEDs... the amount of PAR given off by LED's is very strong on some models and under-rated on the blue colors- so much so that it burns corals. Perhaps the browning is this too?

LED's may looks dimmer to the human eye - but not a PAR meter. Thought I would give that input..

[sphelps]

Originally Posted by chatyak

I haven't read the entire thread - but do you have a PAR meter? Especially if the colors are in the blues on the LEDs... the amount of PAR given off by LED's is very strong on some models and under-rated on the blue colors- so much so that it burns corals. Perhaps the browning is this too?

LED's may looks dimmer to the human eye - but not a PAR meter. Thought I would give that input..

It's a common misconception that a typical PAR meter can be used to accurately measure PAR of LED fixtures. But your are correct that LEDs appear dimmer than other types of lighting due to being a more focused beam and having a more narrow spectrum. However with more full spectrum LED fixtures you tend to get brighter (to the eye) results similar to other types of lighting.

Email from Apogee Instruments on Measuring LED with Quantum Sensor:

"In regards to measuring LEDs with our quantum sensor, there are some caveats to doing so. The following link shows the spectral response of our quantum sensor (http://www.apogeeins...alresponse.html). As the graph shows, Apogee quantum sensors underweight blue light, and as a result, photon flux measurements for blue LEDs will be too low. They also overweight red light up to a wavelength of approximately 650 nm, above which they do not measure, and as a result, photon flux measurement for red LEDs will either be too high (if the LED output is all below 650 nm) or too low (if a non-negligible fraction of the LED output is above 650 nm). Additionally, LEDs often have a very narrow spectral output, with a sharp peak of only a few nanometers. So, unless the quantum sensor has a perfectly flat spectral response, meaning it weights all wavelengths of light exactly the same, there will be errors. Electrically calibrated Apogee quantum sensors will likely provide a reasonable measurement for white LEDs because they are broadband, and because electrically calibrated quantum sensors are calibrated under CWF lamps. However, for narrowband LEDs, like red and blue, Apogee quantum sensors will not provide an accurate measurement.

As a less accurate method you can use the same spectral response graph as mentioned above to get a relative idea of the error. For example, a 450nm blue LED will have a relative response of approximately 0.8. Therefore, you can figure that the photon flux reading from the sensor is reading approximately 20% low. Just remember, this approach is only relative so give yourself a wide margin of potential error. A blue/white configuration should give you reasonable accuracy, particularly from the broadband spectrum of the white.

[chatyak]

Originally Posted by sphelps

It's a common misconception that a typical PAR meter can be used to accurately measure PAR of LED fixtures.

Yes, this is why I stated that it is under-rated, especially on the blue colors.

[sphelps]

Originally Posted by chatyak

Yes, this is why I stated that it is under-rated, especially on the blue colors.

Yes and no. A typical meter will present a lower number for blue only but this number will still be relatively high in comparison to other light sources that appear brighter. The narrow peaks from LEDs in general force higher PAR numbers from a meter while not representing how much of the spectrum range used for photosynthesis is actually being filled.

[Reefer Rob]

I found deep red really adds "depth" to the color of the tank. It makes the corals stand out from the rock, as well as enhancing some of the coral colors (not necessarily red, strangely).

I just added 4 more deep red for a total of 10 at 450mA 2 weeks ago and I really like the look... I think I'm done now. It remains to be seen if I get algae growth with that much red.

BTW with no optics I get no disco that I can tell.