My iPhone has better resolution than anything else I own......but, its major advantage is the I always have it with me, ready to go.
Peter
i agree 100% about the availability of my camera. it's typically not even in the car and my iPhone is generally always close-by.
the real downside is magnification, though. if you're standing next to a train, great, but put any distance between you and the subject and the resolution goes downhill very fast.
here is a cropped image from my Nikon D5100 with my big telephoto lens, though i'm not sure exactly what mag this was taken at, the lens is a 26-300mm...
just a guess, but i believe i was a good 200 yards away from the train.
whereas i was no more than 50 feet from this locomotive taken with my iPhone5...
granted, i was on the wrong side for a good picture anyway, but my point is the resolution.
my camera is fully automatic, but i still have the option of framing the shot with the zoom lens. that's the main advantage i can see.
cheers...gary
