Re: New Xeray XV-LX70. Killer Polarion PH50.
Wow, going to take this light backpacking???!!!! Maybe just a tad over gunned in the lighting department? I've always gone LIGHTER (weight that is!) when backpacking....carrying a spare battery as well? Not sure this was intended to be a backpacking light... Hey Patriot, what say you?
I was reading through the thread again and caught this Karl. Sorry for the initial miss, but this is a favorite subject of mine!
From a practical standpoint no, it's not even remotely a backpacking light, which is pretty self evident as you stated. The LX70 is 5.1lbs and an extra battery is 1.85lbs. That's more than the equivalent of 3L of water weight.
Military and search & rescue would fall into a different needs parameters and enthusiast usage might override any concerns of practicality. In any of these exceptions it really depends on what's trying to be accomplished. Using a light out to extended range, foliage permitting, is the quickest way to navigate "close in" especially when you already have familiarity with an area. I've taken a few night hikes in the Superstition Mtns, where there's usually several landmarks visible with a good light like the Abyss for example. I don't need to look at a map if I can just aim a light and see a familiar rock face, or canyon from a few hundred yards away. If I can get away with a smaller LED light like the TK75, even better. It just depends on how spread out things are. No matter how you look at it though, it should be considered a luxury item for this purpose and depending on the light it might not feel like much of a "luxury" when you're hiking and extra 4lbs up a 1500 ft climb.
These days, topo mapped gps units combined with aerial images can tell us what the topography is around us, so using a powerful light for navigation is a weighty proposal. If you're trying to visually locate a point or object for reasons besides navigation, like finding a downed aircraft in a gorge or spotting wildlife, now we're stuck with the dilemma of which tool to use. All other things being relatively equal, level of performance/capability is directly correlated to weight.
For my uses, I have never taken a large HID or LED on a multi-day trip because my uses would never justify the agony of the load. An overnighter with the support of other hikers might allow for a light up to 1.5lbs if we planned on hiking at night or were going to explore lava tubes or something. The problem becomes having to lug around the weight 8-10 hours a day in exchange for a couple of hours worth of night time capability.
My typical 3 day load consists of an 18650 headlamp and 18650 flashlight totaling about 240 grams.
