Early in the transition to digital cinematography, the inability of digital video cameras to easily achieve shallow depth of field, due to their small image sensors, was initially an issue of frustration for film makers trying to emulate the look of 35mm film. Optical adapters were devised which accomplished this by mounting a larger format lens which projected its image, at the size of the larger format, on a ground glass screen preserving the depth of field. The adapter and lens then mounted on the small format video camera which in turn focused on the ground glass screen.