When the flashlight is switched OFF, Battery Capacity Indicator is activated (Switch LED will be display BLUE) during the following instances.

Hence, 4 BLUE LEDs blinks, followed by a ~1.5 sec pause and another 1 BLUE LEDs blink – signifies 4.1V. I don’t know exactly what ‘Precision Digital Optics Technology’ actually means, but it sounds like marketing speak for ‘a good reflector’. Being coated with crystal should make the lens more scratch resistant though, like decent watch glass. HOLD (~ 1sec) – Light will switch ON to last used mode (last mode memory) – any of the brightness levels (except STROBE, SOS & BEACON mode). There’s a single switch, on the head. It’s an indicating e-switch. I like that it’s bigger than most switches like this. There’s a silicone cover. It also has a strobe feature where the light flashes randomly, a SOS feature (light flashes in the familiar ‘dot-dot-dot dash-dash-dash dot-dot-dot’ sequence) and a beacon setting. These are incredibly useful features to have in an ‘everyday carry’ torch.The E4K is constructed with a CNC machined unibody, making it lightweight, solid and offering excellent heat dissipation. The torch features anti-skid knurling for comfortable grip and cooling fins at the head of the light to reduce weight and for fast heat dissipation. The throw distance refers to the maximum distance at which the flashlight can effectively illuminate an object or target. The stated throw distance typically indicates the point at which the brightness falls below a specified threshold, such as 0.25 lux. The candela per lumen (cd/lm) ratio can be used to determine if a flashlight has a spot or flood type beam. Well-focused spot beams can be over 100 cd/lm, tactical flashlights are typically between 20-100 cd/lm, and work lights are less than 10 cd/lm. Software Modes I’ve taken a good look at the manufacturer information, and a lot of it appears to be a bit of a word salad, but here is the info, straight from the horse’s mouth:

Since the battery has a USB-C charging input port, the flashlight can still be operated if a spare battery is available. The central body of the Nitecore E4K has a non-slip diamond-shaped knurling while in the lower part we find fins of cooling that facilitate the disposal of the heat produced during the use of the E4K at the highest light levels.Here’s a runtime on Turbo. Not that I want the light to cheat for specs, but I’d really like for the initial output to hold on just a little bit longer. At startup, it’s practically 5000 lumens! At… maybe 26 seconds, it’s around 4400 lumens. Then it falls right off. This could have been avoided if a “throwier” LED like the XP-L HI was used instead and would have made full use of the smooth reflector, but at a slightly lower maximum output. Waterproofness