I’m looking for a general formula for how beam throw relates to source lumens & beam angle.
To get that, ideally I’d get specs for at least three flashlights with identical beam angle, beam throw to some specified lux value and lumens or cd or cp.
Then I’d use Excel’s graphing functions to see what kind of relationship, linear or exponential, I’m looking at.
Next best would be similar beam angles (I think I can correct for differences), beam throw to some specified lux and lumens or cd or cp.
Anybody have some candidates for me? Please post links! The specs for different throwers seems to vary somewhat depending on what site I choose.
Once you get out to where the spot is substantially larger than the aperture, its size is equal to the angle in radians (degrees *3.2/180) times the distance, and the pattern stays the same. Its area is the square of the size. The light is conserved, in clear air, so the intensity decreases as the square of the distance. The area of the spot times its intensity is proportional to the part of the light lumens that goes into the spot. You have to look in Wikipedia for the rest of the constants.
also cobsider high lumens does not always equate to large throw.
A c8 xm-l produces far more lumens than a jacobs a60, the a60 will destroy the c8 in throw, same for xp-g vs xm-l.
The xm-l has a wider beam angle than an xp-g, unless you start dedoming, its always going to out throw an xm-l, assuming similar drive currents.
Then you have to look at thermal path. As the emitter heats up, output drops, you could have a hard driven xp-g, and a fairly laid back xm-l but the xp-g may sag almost instantaneously due to poor heat dissipation, hence the craze for direct to copper boards and less so, hosts where the board is screwed into the head.
THEN you have to consider all the other little bits that may hamper output - switch resistance, cell sag, driver cooling, reflector and lense quality, spring contact, spring resistance, quality of thermal pathway, emitter focus,reflector depth and diameter, bezel/beam interference.
Its going to be a big spread sheet, I dont envy you but good luck anyway.
