Among photographers, the idea of cropping photographs seems to be a continuous debate. While some professional photographers state that cropping images goes against their purist ideology, others feel that it can otherwise save a poorly composed photograph. In my experience as a photographer and teacher of design, I find it rare that a poorly constructed photo can be fixed in post-processing. However, that doesn't mean it's impossible either.
Throughout the history of photography, there have been many well-known photographers like Ansel Adams that often cropped their images in the darkroom. In fact, Henri Cartier-Bresson, who was firmly against altering his compositions, occasionally cropped his photographs to create a more pleasing design that followed strict Dynamic Symmetry principles.
Regardless of your ideological views, photographers that want to crop their photos in post-processing will find Dynamic Symmetry to be an extremely useful tool. Also, because the photographer isn't faced with time constraints when designing their images "after-the-fact," I recommend experimenting with the basic armature of the rectangle as well as more complex design schemes that include overlapping root 4 Dynamic Symmetry rectangles in a 1.5 frame. To download a free grid pack for Lightroom and Photoshop, click here.
The photograph above (from a photographer that follows my website) was slightly cropped and adjusted to level the horizon and make better use of the 1.5 Dynamic Symmetry armature.