Again, I would be careful about being so sneaky with the camera. More than anything you are drawing attention to yourself either from the cabin crew or other passengers. If you are approached by the crew it’ll be more difficult to explain that you are just taking pictures for fun after being so sly with your equipment. In our current state of security and crew/passenger alertness I wouldn’t be so quick to act suspicious. I have heard of passengers being pulled off aircraft for such activities. No matter how innocent a passengers intent is the crew doesn’t have much time to explore the “why” of a suspicious activities at the gate so the passenger can be removed so others can figure out why someone was acting as they were.