Firelight2
(Firelight2)
16
To the OP: The Emisar D4 is a great choice. You’ll have a lot of fun with it. It’s my favorite flashlight. 
It’s the ultimate “pocket rocket” with enormous output in a package small enough to everyday-carry in your pocket.
Maximum power on the D4 is really a burst turbo mode. It’s great having a light that can produce 4,000 lumens or more, but recognize that if you need any kind of sustained output, you’re probably going to get around 500 lumens max. The D4’s heatsinking isn’t sufficient to maintain more than that.
Note: A D4 with 18650 tube in your pocket does carry the risk of accidental activation. The button protrudes slightly and if it accidentally depresses the light will ramp up to turbo and stay there. This won’t damage the light at all as the temp sensor in the driver will rapidly ramp output down before any internal damage occurs. However, this may not be in time to prevent damage to your pants. I had a D4 burn through the pockets in a couple pairs of pants due to accidental activation in this way. To prevent this from happening I suggest locking out the light by slightly unscrewing the tailcap when not in use.
If you get comfortable modifying flashlights it is possible to modify the D4 to greatly reduce the risk of accidental activation making tailcap lockout unnecessary.