A major disadvantage of the iPhone—and any other smartphone for that matter—is that it has a wide lens and no zoom. Most apps try to overcome that problem with a zoom function.
Unfortunately that is digital zoom, meaning that you zoom in by throwing pixels away. If you throw away the edge of your photo, the center of your photo seems bigger and therefore it looks as if you have zoomed in. And the problem with digital zoom is that it causes a number of other problems: the subjects in your photos are less sharp, noise will become more obvious and your photos have less pixels. They will therefor look less interesting.
I never use the zoom function in my camera app. In fact, I have hidden the zoom function in Camera+ as I mentioned in an earlier blog post. Sometimes I will crop my photo when I edit it, but most of the time I use Olloclip to zoom into my subjects. Olloclip builds a series of lenses you can clip on your iPhone to change the focal length of your iPhone camera. They have a 2x zoom lens, a couple wide angle lenses and several (7x, 14x, 15x and 21x) macro lens. Lots of options that will help you overcome the lack of a zoom lens on the iPhone.
And with the new lenses for the iPhone 7, Olloclip has added a few interesting features: the clips will work on your front and back camera, you can clip them on over your screen protector, and you can mix and match 2 lenses to your liking.