The Antelope Canyons in the Page, Arizona area, are hugely popular with photographers, and for good reason. They offer unique opportunities to capture the colors, shapes and textures of the sandstone walls and overhangs. The colors change as the sunlight, filtering down through the narrow slots, changes in angle and intensity. The canyons have become something of a cliche for outdoor photographers, but there's no escaping their beauty. If you're in that area, they are definitely worth your time.However, popularity creates problems. Others had warned me how crowded it could be, and I saw them literally trucking in visitors to the Upper Canyon, even in mid-December in freezing weather, so I decided not to shoot there. However, I did enjoy the Lower Antelope Canyon, which is located nearby but which is an entirely separate operation. Go about 11 AM for the best light. A two-hour photographer's pass is $36 and well worth it. You must show them your DSLR camera and a tripod; a point-and-shoot condemns you to touring with a guide and perhaps 8-10 others, all of whom are getting into each others' (and your) way. They are strict about the two-hour limit, but that's enough time if you keep moving.
Shoot with a wide-angle lens at fairly high ISO (400) and don't plan on switching lenses in the canyon: it's very dusty and the sand is extremely fine and can get in everywhere. (One gentleman who was shooting at the same time as me, inexplicably removed his lens and accidentally dropped it onto the sand. We did what could to blow and brush the sand out, but I think he was looking at a professional cleaning.) Take a rocket blower and brush in with you and check your lens occasionally. I used a 12-24mm (DX) lens and was very pleased with the quality of my images. However, a tripod is a must and I recommend a cable or IR remote. Of course, shooting RAW is a good idea, as it usually is elsewhere. Look up, look behind you; walk a few yards and repeat. The possibilities are endless. It's impossible to take too many images.
You'll be moving through some tight spaces, so travel light. I foolishly carried my photo backpack into the canyon, but should have left it in the car. My vest would have been sufficient to carry the few items I really needed. There is some climbing up and down metal stairs and ladders, but if you are careful you can manage them while carrying your camera and tripod.
I processed my images in Lightroom. Because of the variations in light, there can be a large tonal range and lighter areas can quickly blow out. I did not shoot HDR (I'm not a big fan) but Lightroom really did a good job opening up the shadows and toning down the highlights.