Yea, there is, and it gets argued in court at $350 an hour
But yea, it all depends on how similar the shots are. It doesn't have to be exact, or a perfect copy, to end up in court. If its close enough the photographer feels he was infringed, thats all it takes to get him motivated enough to call a lawyer and file suit. Whether its close enough to the original to win is a whole different matter.
Once you are in court, its costly whether they win or loose. So the key is to avoid having something close enough that the original photographer will 'feel' infringed, rightly or wrongly, and decide to take action.
So yes, you can definitely be sued for a 'similar' image, and people have.