In an SLR (Single Lens Reflex) camera, the user is seeing exactly what the camera is seeing through a series of prisms and mirrors. This becomes important for more advanced photographers. In SLR cameras, it is also possible to interchange lenses and keep the lenses from other cameras. Many digital SLR cameras also offer higher resolution since they are aimed at the pros. The disadvantages of SLR digital cameras are the significantly higher costs, bigger size and weight, and a small delay before the photo is taken because the mirror has to move out of the way before a shot.