Now if Apple would let you have full manual control this might be interesting, till then this is just slapping cheap glass onto cheap glass. iPhone is for taking selfies not for anything serious. Canon actually killed their point and shoot line, others are following suit. iPhone Is the replacement and yet is garbage full auto camera. Until that changes this will just be a joke.
You can get apps that let you control the ISO/shutter speed etc.
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They make lenses like these for point-and-shoots too. I have used them, and they're even more awkward. Used to have a tele on my Canon and it literally toppled the thing over because it weighed more.
It got me some good results though. Still ended up selling it.
I have been playing with the idea of getting a DSLR since I got out of high school. There are just better things in life that are better worth dropping that kind of money on. I don't take as many pictures these days either.
You could pick up a real cheap 2nd hand DSLR and lens. Go for it, you'll be amazed at the rests compared to an iPhone.