Take a look at your DSLR camera strap. If you are using the strap that came with your camera, you might notice a little piece of plastic or rubber on one side of the strap. Have you ever wondered what that was for? (If the answer is “No” then it might still be sitting your camera box!)
That device serves a simple purpose that I’d guess 95% of DSLR photographers never consider. Its sole purpose is to cover the eyepiece on your camera and most photographers have never used it, though it can be useful. Even without using that actual device, covering your eyepiece, when your face is not already covering it, can be helpful to gaining proper exposure.
via Cover Your Eyepiece.
