XCam app from XDA devs that's actually free has an paid settings version that enables LG G3 to save photos in full DNG (RAW) format of ~24mb in specific /DCIM/Camera/dng/ directory.
Not many Android devices (only Nexus) have this option, so this is a huge deal for photographers that like to shoot with their smartphones on the go.
Here's a description what you need to have to enable this function. Mostly a pure LG G3 on stock firmware, no need of rooting (only if you want to save photos/videos to SD external card)!
If you decide that you need an option to save your media to SD card then you need to ROOT your device which is really fast and easy with this great script made some time ago.
And here are is the proof that this is the real DNG file/photo and not a fake.