unless the pics are home shoots then they're generally taken in studios or sets designed on site.

if you're talking about the actual scenes in the pics you can generally spot them a mile off lol especially the bondge and in particular suspension ones, look at the positioning of the models bearing in mind that some of the more extreme ones can only be held for a very short period of time and how long does it take even the most proffesional of photographers to get a few good shots, there's usually somebody you dont see either side of the model or rigging supporting the model any shadows, extra support frames etc are airbrushed out and the ropes if you look closely at skin indentations, types of ties,amount of rope used amongst just a few things you soon learn to have a pretty good idea of whats real and whats not.

ok my ''expert'' opinion over lol .. i just couldnt help but reply because so many times IH and myself have looked closely at and laughed at some of those 'genuine' real life pics!