My best advice for Yellowstone (and elsewhere) is to not just view it through a camera lens. It’s better to put down the camera and pick up the binoculars and just watch the wildlife in it’s natural environment. Your photos won’t be any better than the hundreds already posted on Google. If you didn’t take a picture, you still saw it and can always look at the excellent photos already on-line any time you want to. Or just get a postcard and write your feelings about what you saw on the back of it and date it. I know many people have photography as a true hobby, but I just had a small camera that fit in my pocket, and the few pictures I have along with some great experiences tell a story worth so much more to me than hundreds of photos.