One very common phenomenon is that whenever there's something hard to explain in a photograph, most people just attribute it to "photoshop". This is, in fact, the lazy answer to every such picture. It's always "photoshopped".
People are really lazy in their skepticism and are, in my opinion, missing out lots of interesting research that could be done into such photographs. Sure, there are tons and tons of images out there that have been manipulated, but that's not always the true explanation. Sometimes the real explanation is much more interesting.
In many cases the photograph is actually completely genuine and unaltered, but does not depict what it might look like at first glance. A very good example is the so-called "time-traveling hipster" photograph:
This photo was taken in 1941 (at the re-opening of the South Fork Bridge in Gold Bridge, British Columbia). The man looks very out-of-place compared to all the other people around, way too modern, and many claim he's a time traveler.
Of course the lazy default answer people give is "it's photoshopped". But as said, this is just intellectual laziness and complete lack of curiosity on what the actual explanation is. The fact is that the photo is genuine and completely unaltered, but does not depict anything anachronistic.
The sunglasses he's wearing have actually been in use since at least the 1920's, he's wearing a Montreal Maroons sweater (an ice hockey team founded in 1924), and the camera he's holding is probably a Leica model first developed around 1935. His hairstyle isn't unusual for the time period either. The only peculiar thing about the man is that he's not wearing formal wear like most of the other people in the photo.
Another good example is almost any of the numerous photographs allegedly depicting levitation, such as for example:
Again, the lazy answer is "photoshopped". Yet most of these photographs are "genuine" in the sense that they have not been manipulated in any way, nor are they even hiding anything out of view (such as behind the person.)
The crucial thing to understand about this is that this is a still photograph, not a video. If there's any movement happening, we are not seeing it. And that's exactly what's happening: The man is actually jumping from the ground with his thighs / upper legs. The photo has simply been taken when he's at the highest point in the jump, giving the impression like he's just levitating there. (The wrinkles on his shirt are probably a giveaway that he's jumping.)