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.
Opening in the Clouds Panorama
Great Egret Panorama
Cloud Reflections In Water Panorama
Thunderhead Cloud Panorama