In the editing screen, you don't actually crop the photo, but rather designate the area to be shown within the element.
Mask(Crop) Settings. The same window opens when you press the Crop button in the Properties Window on the right.Video elements can also have their displayed areas designated in the same way. Videos with trim applied will only repeat playback within that range in the crop screen preview as well, so you can adjust the crop while watching the actual scene being used.