If the button requires click and drag, like the shutter button for Mattebox on the iPhone, then it's unique compared to the other ordinary shutter buttons, even though visually it's barely different. (Fortunately, it's different enough to indicate what needs to be done — affordance.) That's a fairly unique interaction, certainly within camera apps, that doesn't require much style differentiation.
Using the door handle metaphor, and example would be a handle that's a few inches from the floor and looks almost the same as a handle at 32 inches but is better served by pressing with your foot. Visually the same but very different interactions.
Using the door handle metaphor, and example would be a handle that's a few inches from the floor and looks almost the same as a handle at 32 inches but is better served by pressing with your foot. Visually the same but very different interactions.