Complex sentence: In photography, a sheet of ground glass is used for the manual focusing in some still and motion picture camera taken, the ground-glass viewer is inserted in the back of the camera, and the lens opened to its widest aperture.
Split into simpler sentences: In photography, a sheet of ground glass is used for the manual focusing in some still and motion picture cameras. In such a camera, before the picture is taken, the ground-glass viewer is inserted in the back of the camera, and the lens opened to its widest aperture.