If you're going to crop your images in Photoshop, there's one little button that's pretty new and very important. The Delete Cropped Pixels option does exactly what it says, if checked, it will throw away the cropped out part of your image, never to be seen again! This is how Photoshop worked until a few years ago, called Destructive editing, and is generally not a good way to work. Just as Lightroom works completely in Non-Destructive editing, meaning your original image files are never altered, but simply instructions for their edits are laid on top of the image, you can go back and change them at any time. If you leave this unchecked in Photoshop, and your save your document in .PSD (.JPG will not work), you'll be able to come back and adjust your crop later, with all of your original image still there!