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  1. #1
    Action LED Lights
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    Light Spacial Distribution analysed

    There is always a lot of talk about a given light being a spot beam with good throw or a flood beam with good spill. But other than a beam shot it been hard to quantify and compare one light to another. And unless the beam shots are take in the same place at the same time with the same camera and setting there is no true comparison.
    What light is best for a given type of riding is a question we get asked a lot here at Acton LED Lights. So to give people some good data to make comparisons with, I've started doing some testing I'd like to share.
    My test setup is a 10 x 10 black pop-up with black walls that I set up in the warehouse. The amount of ambient light is small and constant. I am setting the lights up at one side and shining them at the other side 10ft away. A strong fan is blowing on the light. Each light is switched on an allowed to run for 5 minutes until the temperature stabilizes. I use a light meter to find the brightest spot on the opposite wall and then starting there take readings going out horizontally every 1.25 degrees. The results are tabulated and then graphed as LUX vs Angle. For lights with more than one lens/optic option they are presented on the same graph. As a reminder, LUX is light intensity per unit area. You could think of it as lumens per square meter. For a given light with a given lumen output it's light can be concentrated in a tight spot and give a high LUX reading but it will then drop off rapidly to the sides. This will give good throw to light a small area far away. A lower broad distribution is a good flood. I tried to hold the vertical scale the same for all lights for easy comparison but then some ran off the top and I had to reduce the scale a little. So watch to see what the max is when comparing lights.
    I've gotten through most of the lights we sell and will be adding the remaining lights soon.
    I found the result held several surprises. I'll hold my conclusions/opinions for now and see what any of you think.





















    Larger images are available at our website. Light Beam Patterns
    Last edited by Action LED Lights; 03-22-2013 at 12:55 PM.
    Jim Harger
    Action LED Lights
    www.action-led-lights.com

  2. #2
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    Hi Jim, I just noticed this posting and see you now offer an 808 "U". Very interesting. Is there a chance you could compare the "U" version to the 808E? Can you tell if there is a difference in the design of the reflector in the 808U?

  3. #3
    Action LED Lights
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    Hi Cat, I think I do have one 808E left. We've been all U's for a while now.
    I did a quick check when I got the U's for the maximum reading and they were in fact 10% higher than the E's. Magicshine has been using the same reflector since the P7 version. Looking at the light distribution graph for the bare LED, the U compared to the E is unchanged. The only change to the LED was an improved phosphor so that makes sense. I'll still run the E version through the test as well as a P7 and overlay them all for comparison.
    Jim Harger
    Action LED Lights
    www.action-led-lights.com

  4. #4
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    With the gloworm x2, it looks like you are loosing energy at all angles by using a flood optic. Can that be right? You would think that the curve has to higher at some point over the spot-spot configuration as you move from the 0 angle. Otherwise, what's the point of using the flood optic at all?

    On second thought, it looks like there is a small increase in lux as you get outside 10 degrees. Probably not more than 50 lux though. That coincides with a huge decrease in brightness from 0 to 10 degrees though. Hardly seems worth it.

    This probably isn't right, but shouldn't the area under the curve be constant as you switch optics, because the amount of light stays constant? Or maybe it doesn't because the lights intensities are over a circular area, not a straight line.

    I think what you need is to use the lux (which is an intensity) and the angle to calculate the lumens/per degree or something like that. Then plot that value against the angle. That should show that the flood optic actually spreads out the light rather than just decrease it in the center. The area under the curve should be constant.
    Last edited by varider; 03-15-2013 at 09:25 AM.

  5. #5
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    Makes me really happy I went with the Gloworm X1/X2 setup recently. And, according to this, I'm throwing my super spot optic in the X1! It looks like that optic compares VERY favorably against the standard spot. am I reading that accurately?

  6. #6
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    Keep in mind that each lens type will have its own efficiency rating. The physical characteristics of the lenses that cause a wide dispersion of light often create more "optical resistance" or loss of efficiency. In other words, less total light out the front. If the efficiencies were equal between two lenses of different types (i.e. wide vs. spot), tested on the same light head, then you should (in theory) be able to integrate the total area under the curve and come up with the same value for each. Of course this assumes that the "spots" are actually uniformly round. You could not include a asymmetric beam light (i.e. Philips Saferide, etc.) in a test like this.

    Nice tests.... definitely have to appreciate the work that went into producing the plots.

  7. #7
    Action LED Lights
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    Varider, I need to exercise the little grey cells some more but obviously the area under the curves is not equal. This curve is just a 2D slice out of a 3D pie so I plan to compare the volume of the pie and see how that compares. It's more relevant to look at the % increase from one light to another at a given angle.
    I think Pethelman has hit it that there is a difference in efficiency between optics with perhaps the MJ-808U with a reflector being the most efficient. Optics depend on the index of refraction of the acrylic material providing internal reflection and if the light from the LED hits the outside wall at to high of an angle the light leaks out all or in part.
    bad andy, yes, the X1 is a very good example of this. The super spot is brighter at all angles compared to the standard spot. Might as well throw that standard spot away since there is no reason to use it.
    Jim Harger
    Action LED Lights
    www.action-led-lights.com

  8. #8
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    These are very handy charts and are very similar to ones I made about 20 years ago while working for a theatrical spotlight manufacturer. They help visualize the beam angles (it can be noted that beam angle is defined as where the light is 50% of max [center], while field is 10%). From these charts, you can back into the center-beam candlepower value, thus making it easy to calculate illuminance at a distance using the Inverse Square Law. You can see similar data published by major lamp manufacturers (GE, Sylvania, Philips, etc) on all projector-type lamps.

    Basically, in all aspects of the lighting industry except flashlights and bike lights, manufacturers publish photometric reports so that you can compare the performance of their lights to their competitors. As someone fairly knowledgeable in lighting, I am starved for data like that published above, so thank you. Frankly, I am more inclined to purchase a light from a manufacturer who publishes their photometrics than one who does not.

    One comment about your notes on top: Lux is lumens per square meter; footcandles is lumens per square foot. There are about 10.76 square feet in a square meter. Also, the light measure is incident (illuminance), as opposed to reflected (luminance). In the case of these charts and measurements, I think you can skip Cosine Correction (which accounts for the longer distance the photon travels off nadir to the measurement point).

    Thanks for doing this, and keep up the good work.

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