If the dross on the edge doesn't contribute to the image, it needs to be cropped out in my mind. And by defining it as dross, you are saying it is unimportant. I would say you are being lazy in making the viewer pick out the scene in the image that you saw when you took the shot. My first thought when I see an image like that is: "he should have cropped that down; it could have been a strong image" Frequently I am saying that about my own images months in the future when I notice the dross that I wasn't focused on when i was printing.
Originally Posted by cliveh
I usually print a full frame version though so I can live with it for a bit before I decide on the final cropping. Make some cropping squares (L shaped pieces of paper) and try out many crops. I think each image will have a strongest crop, and it usually isn't what the camera dictated.