They're not photoshopped, they're works of art.
I saw a program once where several groups competed to make the most intricate designs, some were really artful. It also explained how they are made, and how to hide your tracks in the cornfield if you ever want to make your own, lol.
I do think that most of the cropcircles are the works of humans. Some however can be works of nature. there have been some that have been proven to be caused by "mini-tornadoes", like dust-devils. Those look very "primitive" though, just rough circle like patterns in the grass or other vegetation.
Maybe that's where people got the idea for the faked ones.
There's also a program that was on some time ago, where they interviewed to men from Britain, who claimed to be the ones to start the whole rage, and they explained how they made them with just a wooden board and some strings.