I used torches in the army and also contracting in half a dozen countries. One of my lecture posts coming up. Strap in or scroll past, whatever suits
The important measurements are lumens and candela(CD). Lumens is how much light total, candela is how much range the light has( dictated partly by lumens but also LED type, size, shape and smoothness of the reflector) Candela is more important for long range, a lot of people forget to check this, it will tell you how far the torch shines.
Examples
Generally small lights, work lights or paramedics duty lights might be high lumen, low candela, to light up large areas in close, high flood, low spot. Candela might be only 3000-10,000 Cd.
10,000-20,000CD is more medium range(illuminates to solid 30-70m), mix of flood and spot.
Torches over 30,000CD are starting to get into longer ranges, up to about 90,000( illuminating (70-200m). Hunting torches usually start here.
Long range setups. Figures as high as 250,000. CD etc, 250 m+. Keep in mind high CD may mean a very concentrated hotspot with little or no flood. if you want a mix check the beamshots of the torch on youtube, almost everything is reviewed there.
Note manufacturers maximum distance claims are always about 2.5-3x worse in real life. That's because their test goes off an obscure scientific test of 1 unit of illumination at that range, which is beyond normal human eye use. If they say the torch is good for 200m, its more like 70-80m in real life.
Torches with variable spots and flood are okay but usually don't have the best of either, waste some lumens doing so, and may have have lesser IPX( waterproof and durability ratings) to be able to do that. Led lenser became very popular with this in the 2000's but serious light users these days more often choose regular beams.
IPX ratings relate to dust, shock, immersion, drop proofness. IPX8 is the highest, realistically everything is IPX8 these days.
Make sure the torch has the interface you need. A lot of the light market is powered by whats called 'flashaholics' which is people, often teens, who buy and review torches just to have torches. This has generated a lot of torches with excessive buttons, extra functions, dozens of light modes, crap like strobes, SOS beacons, to keep them happy. Ensure to check the torches interface in the store or on youtube to make sure its handy for you. I find about 90% on the market annoying to use. You may be cycling through light levels you don't need, activating beacons for holding the button in too long etc just when you want to shoot a pig that appears. Generally the remote switch in dedicated hunting torches will alleviate a lot of this.
Generally I find the best interaction for handheld is what military and cops use. At least one button than can do simple on/off, that can be set to immediately turn on at high, and a momentary function( meaning you can slightly depress it to flash it on and off, without clicking it fully on).
batteries. 18650 rechargeables are the go-to these days In the 2000's the 18650 battery powered torches for hours, as lumens technology was still embryonic. Then around 2014 they both complimented each other, lumen levels for a handheld for example were about 700-800 lumens which still gave you 1-2 hours use. Now lumens have far outstripped 18650 capacity. All it means is when you buy a torch stating crazy 1600 lumens just be aware that at full power it will suck the battery faster, also heat up the torch a lot. Some of these figures are using a "turbo setting" too, which only runs a few minutes so it doesn't fry the torch. Check reviews to make sure the light level you want, lasts as long as you want. My personal opinion is for over 1000 lumens I like a torch in 2x 18650 confguration for more capacity.
2 x 18650 torches should have the batteries paired or mated for life. If you replace the batteries for recharging, replace with a new complete mated pair, and recharge the other ones together. This is because lithium batteries get a memory and if they discharge at different rates with an odd battery it can potentially and extremely rarely cause fires in the device.
Quality levels are as follows.
1. Custom manufacturers and top end US brands like Surefire, Pflexpro, malkoff, HDS, macgizmo, Elzetta. Usually lifetime warranties, big dollars, and potted electronics( electronics often encased in a potted compound to offer more resistance to recoil and impact)
2. High grade chinese brands. Olight, Klarus, Armytek, sunwayman, nitecore, eagletac, led lenser etc(german owned but now made in China), wolf eyes( australian designed). As good as no.1 usually, not as often potted electronics. This is go-to for most duty users, hunters etc, warranties usually 5-10 years and they are affordable. Normal stuff with chinese goods, you may get the bad one and have to send it back...
3. 2nd tier or budget chinese brands like microfire, xtrafire, jetbeam, convoy( too many names to list). Sometimes great, sometimes not as great. Candlepower forums are the experts on lights btw and another site 'Budget light forums' are a good source for reviews on the budget stuff to see how it goes.
4. Kmart, fishing store crap.
What else? Magnetic mounts. I didn't like them.They can be bumped off in the scrub, they also swing around smooth barrels during recoil( as in rotate around the barrel, changing position).