“To be, or not to be, that is the question…”—William Shakespeare’s Hamlet.
You can always use Photoshop to crop an image after you make it to produce the exact image you had in your mind but when you do there is a price to be paid. You are tossing away pixels. This is what’s wrong with the so-called “digital zoom” functions that many cameras have. Yeah, you get the image you want but the resolution is less. So take a tip from me: Crop in camera when you can.
If you have a Zoom lens use it to frame the image exactly the way you want before tripping the shutter. If you don’t have a zoom lens use your feet as a zoom and move around to get the subject framed just the way you want. Often taking a single step closer to our subject will improve the composition more than you might otherwise think. Don’t believe me, try it! Don’t forget what Ernst Haas once said, “The most important lens you have is your legs.”
If neither of these alternatives works with a given photographic situation use the Crop tool sparingly. And on the few occasions when I do crop (and I am being less dogmatic about this as I get older) I use the Original Ratio option, keeping the image the same shape as the original file. OK, sometime, with landscapes I jump on the 16:9 ratio because I love that wide-screen and HD video look.
Tip, if you want to hedge your best, use the Image Size controls and check the Resample Image using the Bicubic Automatic option. A few years ago I tested a bunch of resizing programs and found that in a blind test Photoshop’s Bicubic scored as high as external programs.
But remember there is no free digital lunch. Every pixel you crop out is one that is lost forever.