Do you already know what optics you would like to use? It would be great if it was compatible with Yajiamei optics.
For example with this: Frosted Yajiamei optics
Then, my suggestions for 20mm × 12.8mm Yajiamei optics:
Clear surface:
- all of them should be checked for each unique LEDs to be used with, because beam artifacts would be visible depending on light emitting surface shape and textures
- also, less suitable to mix tint of the LED
- 5 degree variant gives the most throw
negligible spill outside the hotspot, most of the light is focused in the hotspot (or there is a small corona as well)
Beaded surface:
- handles the different LED emitting surfaces very good, mixes tint better
- negligible spill, but it is a bit more than spill of the clear surface, also, slightly textured
my personal choices: 10 or 15 degree gives very good throw; 25 degree is the best for general usage; 38 degree is a bit floody, above that, definitely floody, but still defined hotspot
Frosted surface:
- handles different LED emitting surfaces very well, even the worse ones (best tint mixing ability)
- much more light is present in the spill
my personal choices: 15 degree gives a nice, conical profile gradually strengthening hotspot, 30 degree is already noticeably floodier; 85 degree feels like an extreme flooder (almost no hotspot perceived)
I regularly use Yajiamei optics in S2+, so my recommendations would go for:
flashlight: 10 and 25 degree beaded, 15 degree frosted
headlamp: 38 degree beaded, 30 degree frosted (also, 60 degree beaded and 45 degree frosted, if more flood is required - e.g. for close range hand work)
Simon the S11 is a nice size. Easier to hold for me and offers some more heat sinking. The upcoming 21700 S2+ will be sure to please. I wanted to share that a 20mm driver would fit into the driver ring if it is flipped over and soldered. Thanks.