If I'm allowed a blasphemous suggestion.
If you have a work phone and a personal phone, you're in luck.
Consider the combined weight of the office Blackberry & your personal iPhone, versus iphone + charger.
Decouple the GPS from camera from the phone. In the case of the iphone where you cannot take a spare battery.
Compare the weight penalty of taking 3 separate devices, versus taking 1 smart phone and 1 charger.
You can take as many photos without worrying that you will run out of battery power for cell phone emergency.
You don't have to worry about the GPS or the phone roaming and draining either.
you can keep your phone turned off until you need to power it up.
In some cases, the redundancy is nice to have, even at a cost of extra weight.
I'm a Murphy's law guy. The elusive Big Foot will get carried away by a presumed extinct dinosaur bird, as soon as my battery goes dead, and I miss the Pulitzer shot.
On another trip, my friend dropped his Smart phone stepping out of the truck at the trailhead, cracked the screen, and was S* out of luck the rest of the trip. His wife was worried he didn't call, he had no camera to document the adventure... you get the point.
Not ultra light, but real life.