Goal is to find 18650 or 21700 light with very pleasing beam pattern, with regard to hotspot angle, spill width, and ratio of output in spill/hotspot. I like W1 emitter in P60 reflector except that the spill is rather narrow, which I believe is due to the depth of the reflector.
Comparison of beam shots in reviews shows that Emisar D1 has one of the widest spills and is capable of tight hotspot.
I used the calculator here: https://budgetlightforum.com/t/-/48052. My assumption is that relative comparison of beam divergence angle indicates relative angle of hotspot. I input reflector diameters of P60 and D1, and played with focal length until the reflector depth matched the measured dimensions (found online in reviews and product specs). Is this the right way to do it?
I input LED diameter as diagonal length of die, and came up with the following beam divergence half angles in deg.
519a DD 15.1
This suggests that W2 in D1 host will have similar hotspot angle as W1 in P60.
Is this sound logic?
What I don’t understand is why the calculated beam divergence seems so off. For example, Zebralight specs SC64c LE as 12 deg hotspot, and that is a very floody light. Surely way floodier than 519a DD in D1, which was calculated as 15.1 deg.
Am I misunderstanding the meaning of beam divergence? Or is the problem with the focal length?
D1 reflector: OD 30.5 mm, center hole 7 mm, focal length 2.55 gives approx. reflector length of just over 20 mm (matching TG reviews measurements).
P60 reflector: OD 26 mm, center hole 7 mm, focal length 1.85 mm gives approx. reflector length of 22 mm (matching specs on Kaidomain product page).