Although not an extreme ultralight backpacker, I follow those principles for what I take with me and I like to move fast in the high mountains. I don’t go to take photos, I go for the experience, but good photos are a plus. I can get some great photos with my phone at this point, though it certainly isn’t the same as a DSLR camera. My phone has my maps for navigation and my books for reading in camp as well. It’s waterproof and resilient and weighs very little. It is extremely convenient for use - put in pocket, take out when needed.