The Beam profile thread...

LED Flashlights – General Info
1

The more and more I get into flashlights & torches, the more and more I’m convinced it’s easy to get muddled up with the terminology and talk about different beam types, e.g.

-floody
-thower
-beam distance
-hot spot
-spill

And so on.

So maybe this would be a good place to try and solve the myths and help add clarity to the meanings.

On thing I’ve picked up on recently is what do people mean when they say “floody”?

I think this can often be taken several ways, but which is really correct.

e.g.

Does the size of the hot spot make any different to weather a light is floody or not?

How about the size of the spill beam?

Or how about the transition between the hot spot and the spill?

Do any of these on their own make for a floody light, or is it a mix of all three?

In this picture there are 4 beam shots (make belief) that you may see from a SMO reflector torch.

On the left you have a small hot spot, which means likely a smaller emitter and/or tighter focused beam (location of the LED in relation to the reflector like the MagLite focus). And a small spill beam, which means a relatively deep reflector for it’s diameter. This looks a lot like my EagleTac D25LC2 with an XP-G.

The 2nd from left has a larger hot spot, so more likely an XM-L over an XP-G or XP-E. But the spill is the same size. Or it could just be a slightly defocused smaller emitter.

The 2nd from right is very different. It has a small hot spot but a large spill. Which would mean a far more shallower reflector in relation to it’s diameter and LED size This beam resembles that of my 1xAAA Tank007 EO9. Amazing throw for it’s size, but also a massive wide spill beam, although the spill isn’t massively bright.

The far right beam just has a bigger hot spot again.

So which, if any of these would be a “floody” beam?

To make matter more complex, if we introduced a OP or HOP reflector you could turn either of the left (small spill beam) images into smooth gradual transition from spill to hot spot, creating a far more even lighting effect. My Klarus NT20 would be a good example of this, it has a reflector (in size) and emitter that matches my EagleTac D25LC2 but is heavily orange pealed and looks totally different in terms of beam.

Questions:

Is flood about:

-the evenness of the illuminated area?
-the angle of illuminated area?

For example, anyone who owns an A8 BLF Edition will know that is has a very large quite unfocused XM-L hot sport, that has quite a smooth (if ringy) transition into spill. This means it’s spill is also very bright. But due to a fairly deep reflector and a very pronounced deep bezel it means the diameter of the spill beam is actually very small.

How should such a light be referenced in its degree of floodiness?

2

Good points. I think that words like flood and throw are inherently subjective and can only be used when comparing one beam with another or generally classifying a beam. To actually quantify the output you need either more words with parameters for defining beam types or numbers that do the same thing. One standard is FWHM or full width half maximum which is the half angle at which beam intensity drops to 50(why this is *full width*I haven’t a clue unless it’s the half angle at which 50 of the total output in lumens us contained in the full width) . This is often in addition to a plot showing the intensity vs beam angle. These are easy to understand visually but harder to convey in words. Given the arguments that ensue over words that already have scientific definitions, I wish you luck coming up with a set of your own and finding a consensus on them.

3

I had some trouble with terminology. It can be quite subjective too. A beam shot doesn’t quite cover how the light feels in use.

I would say the unfocused beam of a Sipik SK-68 is very floody. It is a bit more even than this to look at in person:

But the beam of a Tank007 TK-703 is more spill and hotspot. I do not consider this to be a floody beam as the hotspot is quite intense, even too bright for close up tasks. This concentrated spot of light is useful, however, at greater distances. The deep reflector helps it to “throw” light. In use, there is a bit more spill than appears here:

4

I did not take all the “typical beam types”. But here is how I would describe some of the more common ones.


(sorry about the size differences, I had to chop it into two pictures)

5

anyone got a shot of an MCE LED 4500k?
thanks.

6

I’ve been trying to come up with a way to create plots representing beam profile. Something like log(lux) on the y axis and angular displacement from –30 degrees to +30 degrees on the x axis. Or, you could use a circular graph, like an antenna field strength plot.

I’d love to be able to overlay two or more such plots from different lights to compare.

7

So someone made progress on this as i just came across

in a recent review.