Sometimes when I am walking around with just one camera with one lens, I come upon an image that is too wide for the lens I have with me. Or I see an image that is perfect for a panorama, but I invision a longer thin crop without a lot of extra image that detracts from what I want. I also do not want to crop my panorama from my regular file because I want a large image, either for a double page spread or maybe a large print, and want to hold the detail with all the added pixels. Most often I make panoramas with my 300 or 400mm telephoto, 24-105mm or one of my macro lenses for a macro panorama. I have not had great success with my 12-24mm zoom. Usually for simple panos I shoot 2 or 3 images for combining, but have gone up to 60 for very long or a series of multi-exposures for different rows of stacked panos for one image. I use Photoshop to render my panoramas and after practice you can get predictable results most of the time.