Digital Single Lens Reflex camera, has a mirror inside the camera body. It allows you to see the scene through the optical viewfinder and the camera body that allows light to enter a single lens where it hits a mirror that reflects the light either upwards or downward into the camera’s viewfinder. When you press the shutter to take the photo, the mirror flips up out of the way. You can add additional lenses to a DSLR camera. Even a 15-year-old autofocus or 40-year-old manual focus lens can be used, depending on your camera. You can turn it on very quickly and take a picture right after pressing the button. DSLR tends to be large and heavy have and it has a lot of motors and mechanics which make the same noise.