It is necessary to take a SLR when traveling, and a good shoulder bag is still necessary.

Of course, a good backpack is necessary, but it also has its troubles. Inconvenient. SLR cameras are compact and elegant, and easy to shoot. You can take it with you when not in use. If you carry a backpack, you can't put it in. If you leave your SLR in your backpack when you are having fun, of course you are in trouble. . . .