The viewing lens projects an image onto a viewing display screen which can be seen from above. Some producers similar to Mamiya also supplied a reflex head to attach to the viewing display to allow the camera to be held to the eye when in use. The benefit of a TLR was that it could be easily focussed utilizing the viewing display and that beneath most circumstances the view seen within the viewing display screen was identical to that recorded on movie. At shut distances however, parallax errors were encountered and some cameras additionally included an indicator to show what a half of the composition would be excluded.

The design and manufacture of the lens is important to the quality of the photograph being taken...