For most point-and-shoot cameras, the viewfinder is near the top of the camera close to the lens. The image seen in the viewfinder is not exactly the same as what will actually be captured on the film. Thus, it can be important to make sure the subject you’re interested in photographing is somewhere near the center of the viewfinder’s view.
With single-lens-reflex (SLR) cameras , the image that’s seen through the viewfinder is the exact same one that will be captured onto the film (or onto the CCD [the electronic ‘film’] in the case of digital SLR cameras) .
The viewfinder for my camera.
UV filters are also a good idea to simply keep on your camera because they also protect the camera’s lens from dust and other things that can obscure the image or damage the lens. It is far cheaper to replace a UV filter than it is to replace a lens.