When I am planning mods I think about the beam shape and how to optimize it for a given purpose. To help me see all of my modded lights and how their beam characteristics relate to each other, I made this plot. The x-axis is the total light output of a light and the y-axis is the peak beam intensity. Each light is represented by a point in this “throw/output” parameter space.


The beam size comes naturally out of these data. The luminous intensity in candela is the lumens per solid angle (steradian), so if one divides the total output by the luminous intensity one gets the solid angle of the beam. There is then just some math conversion to get the beam width in degrees. The grey lines in the plot represent different beam widths. This derivation of the beam width is accurate for a light where all of the light is within the beam, and the beam is uniform in intensity. The beam of a lens thrower is like this, but for a typical light there is some light in the spill and the beam is not completely uniform. So for a typical reflector light the actual beam width is a bit smaller than the above derivation would indicate. But this is still a good way to easily compare lights with very different beams.


In this table are the data for the lights in the plot. The lumen measurements are from ceiling bounce, so they are estimates with ~10% uncertainty. The lux measurements are taken at 6m. They are all direct drive with a typical high drain cell(s).

I also have two lights in the table that I am thinking about making, the quad XPG2 or XPL C8. The quad XPL would essentially be my big 7xXPL L2 at half power. I would use a supfire L6 host (26650 sized C8). The quad XPG2 would be in a convoy C8 host with tube bored to fit a 20700 cell. Both would be very cool lights I think.

I think the plot is a neat way to see how very different lights compare to each other. I have had a preference for making lights with a ~15degree beam size. This is partly because I find this to be a useful size; a compromise between providing some good throw while not being too narrow to use up closer. It’s also because of the availability of the 17mm narrow beam TIRs, like used in the S2+.

Anyway, I just wanted to share. I hope you found it interesting.

Originally posted BudgetLightForum.com on May 4, 2017.