Consider how far away you can see, even with a light. Usually anything more than a few hundred meters is overkill.
I would be looking at a smaller, 21700 light with a 4000k emitter and reasonable throw.
Also, I think a reflective harness on the dog, together with an illuminated collar or fob would make it a great deal more effective.
Take a look at the Sofirn SP70. Lots of light. But a bit heavy.
Also the Streamlight Protac HL 5-X. The TIR front end give a different spot and spill.
I did a review here
All the Best,
Jeff
Thanks for clarifying. I guess keeping track of your dog and actively using the light to search for people are quite different use cases.
In terms of reflection from trees and the like. I sort of get what you mean, but without being there to experience it, I guess it is difficult to really grasp how much of an issue this is and how much is beam profile vs tint etc.
A thin beam will allow you to shine ‘through’ the trees some what. But a more intense hot spot is likely to reflect back at you more intently too. I suspect a floody light does light up more in trees but where the light doesn’t reach will appear darker and the trees you are lighting up will cause shadows behind them. I wonder if this is more the issue?
As for which light……
The L21A is a great light with the W2 HX LED. And for the money it is good value for money. But they are only available in cool white. But it isn’t a horrid colour. In trees I’d assume your distance/line of sight is actually rather limited. So I’m still not sure how useful the beam would actually be. As closer up the beam is smaller.
A plus point for the L21A is the 21700 battery and heatsinking. These will give good long runtimes without ramping.
A major downside IMO is the balance and weight of the light. They are head heavy, so it won’t just ‘sit’ in your hand. You will actively have to point it and hold it up. I think for prolonged use this would get very tiring and weighty.
Maybe the M21 or a C8 with the same LED in would be nicer to hold and carry. And still offer the right type of beam?
I guess the FT03 SST-40 might work too. Not a dedicated thrower, but nicer to carry than the L21A. More of a traditional beam profile. Good spill, but fairly intense hotspot and moderately good throw.
The KR1 would also fit the budget, the most easy to carry and pocket friendly. But an 18650 will give lower runtimes (same with the C8). KR1 is smaller, so will heat up more if using Turbo.
Lastly and thinking out of the box a little. YLP Falcon F15:
https://ylplight.com/en/katalog/1/falcon-f15/
Now this won’t be a throw monster. But the zoomy head will let you focus the beam for when you are in the trees. And the throw is pretty good for this size class. Should be easy and comfy to hold and carry too. And the lower output/amps mean runtimes on an 18650 will be better than the KR1/C8 with the Osram LEDs. I think there is a BLF code for these too.
I’m a dog handler as well. For me, I keep different lights with me or in my truck, I probably use my acebeam T27 the most.
You get my problem straight to the point 
I think I’ll have to try different lights to see whats the best for me.
One thing i haven’t known was the problem with the reflection of cw light, thank you all for mention that.
It’s clear for me to use different lights in different situations. For close range I already have lights I’m happy with, but i have nothing for longe range.
The T27 has realy nice beamshots. Thanks for that.
CW definitely scatters more and causes harsher reflections. BUT, and this is coming from a hi-CRI obsessed person, sometimes it’s better at showing contrast. I find in the winter here in the snowy Appalachian woods, where you have three colors… Brown, white, and darkness. I’ve found that when everything is shades of brown, somehow the color fidelity issues with some CW LEDs actually help add contrast. I wish I could take good pictures to show what I mean, and YMMV. If I were to try to explain it another way… for me, the ‘greyscale’ is easier to pick out objects than with a ‘brownscale’.
Best advice I have is to try different lights. Check the FS adds and see what you can get cheap. Lightbringer mentioned a zoomie called a Jaxman Z1, that’s good advice for you IMO. If you’re so inclined, it’s a great easy host to start doing emitter swaps and figure out what works best for your environment, eyes, and taste. You can put a range of emitters in that host and have anything from a 300+kcd thrower to a high lumen even flood light.
Best advice in the thread though is a reflective harness/vest for your dog. An AA maglite could work at 150m in that case haha
Cheers!
I’d look at the Nitecore MH20GT but they don’t make them any more. It’s got that great combination of light weight and great throw (hence the GT on the end of the part number). The Nitecore replacement isn’t as good IMO. As an aside, I just bought some of these cheap things, less than $2 each US, for my dog -if I was lost in the woods in the dark it would make your dog visible to me.