Just so you know, there are two Antelope Canyons--Upper & Lower. In the Upper one, it is level and you just walk right in. In the Lower one, you climb down a ladder from one of the openings in the top. Initially we had intended to do both, but once we did the Upper and got tons of pictures, we didn't feel the need to do the Lower one.
We weren't on a photo tour and used just a point-and-shoot camera, but the photos were incredible. Try to arrange your time so that you are inside around noon because the shafts of sunlight coming straight down make for some really cool pictures.
Since the canyons are on Navajo land, you have to go in with a guide. We
just drove there ourselves, paid the fees, and went inside with the guide. It was possible to make arrangements on site for a photo tour the next day.