I have had a revelation myself maybe it's the stain that is the defining factor lol..........Just kidding.......Glad to hear they are on the warm side, should help a lot come the 2nd stage.
With regards to the light debate I thought I would add a little bit more fuel to the fire,
"Default Re: Lux, Throw, Beamspread, Inverse Square Law etc.
Measuring light has turned out to be a very interesting task…
We are observing that there are a lot of variations in our light meters with broad spectrum measurements, and the filters used in the meters seem to be quite different in sensitivity to spectrum peaks at differing colors.
Since the subject of throw has been brought up, let’s take a moment to define just what throw really is.
The general purpose of a flashlight is to illuminate something. The brighter the light, the further away we can be and still illuminate the object we are looking at. This is where throw comes in. Doug (Quickbeam) is measuring light at 1 meter and reporting a lux value. Through the inverse square law, we can calculate the distance (in meters) that the illumination will drop to 1 lux, by simply taking the square root of the number recorded at 1 meter.
The reason we normalize everything to 1 meter is because lux at 1 meter (or foot candles at 1 foot) is equal to candela, and the square root of candela gives us the distance in meters that the light drops to 1 lux (or the distance in feet that the light drops to 1 foot candle).
It has been pointed out that some of the lights may not fully develop their beam at 1 meter and the readings will be off utilizing this method. This is true.
In general, the minimum distance to take a lux measurement should be at a distance at least 5 X the diameter of the source. If you have a light with a 27mm reflector, your minimum distance should be greater than 135mm. If your light has a 223mm reflector, you should be at least 1115mm away. In this later case, you end up more than a meter away.
This is a good general rule, but I like to take it a step further. Borrowing from the laser technology, we can look at the beam and make an effort to determine its waist dimension. The beam waist is the minimum diameter (or radius) of the beam. Once we calculate the beam area at the beam waist, we can them move on to the Rayleigh length. The Rayleigh length is the distance from the beam waist where the beam area has doubled.
It just so happens that the beam beyond the Rayleigh length behaves according to the inverse square law.
How does this apply to our measurements?
I think we have a couple of solutions. We can measure the minimum beam diameter and move out to beyond where it doubles. We can then normalize the readings to 1 meter for comparison and take the square root of that value to determine the distance the light illumination will drop to 1 lux.
On the other hand, we can simply set the light up on a tripod and walk away from it until the meter reads 1 lux. Measuring the distance back to the light will give us the throw distance down to 1 lux.
Concerns over the artifacts or smoothness of the beam being measured are not well founded. The meter manufacturers have thought of this ahead of time and the meter sensor is covered with an integration dome. This integration of the beam tends to cancel out any artifacts present in the beam.
All of this is nice and tidy, however, as has been mentioned before, this all applies to a “point” source. The definition of a point source is relative. At 10mm, the filament of a lamp or the die of an LED will hardly appear as a point source, however, if you move back several meters, they begin to approach a point. At a kilometer or two, I believe everyone would agree that they appear as a point source. This seems to suggest, to me at least, that we will get more accurate readings at greater distances.
In addition to the point source issue, adding optics and reflectors allow the light to be manipulated in ways that can distort the inverse square law. Since most of our lights have optics, lenses, or reflectors, I am once again under the impression that measurements taken at greater distances may offer more accurate estimations of what is actually going on.
I have personally demonstrated the inverse square law by taking a measurement at a close distance, calculated the distance I needed to go to get to 1 lux, then taken a measurement at that distance to see how close to 1 lux I was. Generally, I find the results are pretty close to the calculated values. The key to this seems to be to take the first measurement outside the Rayleigh length.
These measurements provide a good approximation that allows us to compare various lights. As with all approximations, there may be some issues with some individual lights, but for the most part, I think it gives us some valuable information.
Tom"
"Man Tom ... that was good
Does this mean then that if I follow your orders correctly I can apply the inverse square law to any light I own? And it will be representative of throw then?
Extreme example:
I have a room light incan bulb which produces a completely uncollimated beam and we assume it produces 500 lux. The competitor is a reflectored incan light that also produces 500 lux but has a very much collimated beam. Evenmore extreme ... what if I had a laser with virtually no beam divergence?
Now ... will both (or all three) throw the same distance?
bernie"
"Hello Bernie,
To the best of my knowledge, that is correct.
Even lasers follow the inverse square law once you get out beyond their Rayleigh length.
Columating reflectors and focusing optics and lenses distort things in the near field, but once you get out to the far field, the inverse square law takes over.
Tom"
