You should add something about medium format and maybe even large format as well. not that most people would consider either, but just for completeness. also why no mention of the advantages of prime lenses. it seems that for lower weight, a lot of hikers would do fine with a slr and a 50mm prime. they weigh less, and stop down a lot faster, and it is one less thing for people to think about, not to mention the better image quality.