Beam Angle Graph Feedback

Hi everyone! I'm making a new graph(s) to put into my flashlight reviews and wanted to see if makes sense to anyone besides me and/or if it seems helpful or not.

I'm plotting light intensity versus angle away from the center of the beam. I believe this will help folks get a better feeling of how floody or throwy the light is. Many times, especially for headlamps, a wide beam angle is advertised but often the light intensity of the spill is far dimmer compared to the spot.

I've made 2 graphs showing the same thing. First is a polar graph which simulates what you might actually see coming out of a flashlight. One draw back is that the very dim levels of spill aren't very readable. How important is a few lumens of spill? I'm not sure.

The second graph is a 'rectangular' graph which shows some of the lower spill levels but is not in a realistic beam shape.

Do both help?

Any thoughts are much appreciated!

I like the idea, maybe for the first graph just use the upper half. It would be a nice tool to compare different flashlights and I think the second graph adds the information missing to the first graph.

But I think what you need as addition to this two graphs is a beamshot right next to it so the viewer relate those three images to a beam profile.

rayman said:

I like the idea, maybe for the first graph just use the upper half. It would be a nice tool to compare different flashlights and I think the second graph adds the information missing to the first graph.

But I think what you need as addition to this two graphs is a beamshot right next to it so the viewer relate those three images to a beam profile.

Click to expand...

Cool thanks 👍 glad they make sense. Yeah forgot to say I'd include the graphs with my typical pics of wall shots, but I like your idea of side by side for easier comparison. Do you think the wall pic should be the height of one or both graphs? Or should it be 3 side by side pics? Thanks!

Why 0% at the bottom and 100% at the top? (Bottom graph)
Light fall off?

Imo the bottom one next to a beamshot would be easy to discern. Same height as the photo.
Perhaps instead of % to the left an approximate distance?

I don't get the circle graph. Well, I do but the bottom graph seems more relevant for what you are trying to show.

The way the angles subtend on the top graph makes it hard to get an indication of the beam profile (at least in close to your 0%), so your lower graph is the most useful (to me). Great idea for sure, too many companies don't give a spot or beam angle. If you got rid of the lower half of your upper graph, maybe you could increase the size of it for easier reading by old people like me

+1 on throwing the distance in with your percentages.

Cheers!

Well, I'm an engineer, so I understand both graphs and like having both of them. The top one looks more intuitively like what you'd see if you laid the light on a table, effectively getting a cross-section of the beam, and the bottom one provides more resolution when you're trying to read brightness levels futher out from the centre spot.

If I had to pick one or the other, I'd choose the bottom graph.

On a related note, for light sources with a symmetric emission profile, you can draw a composite graph, by taking the upper-left quadrant of the top graph and the right side of the bottom graph and butting the two together side by side. That way, you get all of the information in half the space.

I now find myself speculating on whether it would be worth using the square root of intensity on that scale, to reflect throw as seen by the human eye, on the basis that four times the intensity only lets you see twice as far. Mind you, that would just be another way of getting the throw distance curve that previous posters have already suggested; the curves would have the same shape.

I think beam angle graphs are important. They provide important information. For example, the Eagletac MX25L4Cvn and the K60vn have almost identical lumen and throw specs, but they have vastly different emitter configuration. Beam angle graphs would show the differences in the beam profile.

Compare beam profiles of different lights with similar specs? candlepowerforums.com/vb/showthread.php?423659-Interpreting-specs-Compare-beam-profiles-of-different-lights-with-similar-specs

CivilGear said:

Do you think the wall pic should be the height of one or both graphs? Or should it be 3 side by side pics? Thanks!

Click to expand...

I think the best would be to try it out and see what is best, but side by side sounds promising.

What an interesting kind of information about beam that you'll never find elsewhere!
Very apprecciated thanks!

I definitely favor the bottom one.
I assume that 100% correlates to the maximum light meter reading at the center of the beam. And, the other points plotted are also direct readings of the light meter. Remembering that we actually see the square root of these readings, I wonder if the bottom graph would be more telling if the square root of the readings were plotted?

BTW, this is extremely useful information because, as you say, lumens & lux do not adequately tell the story.

Wow thanks for all the feedback everyone! I didn't know about the square root factor, I'll have to look into that 👍 In the meantime I included these charts in a recent review I did for nitecore NU25 headlamp which has a main and secondary light see here if interested https://www.candlepowerforums.com/threads/443955
[Review] NItecore NU25 Headlamp ... 360lm + USB charging + reading light