Technical
Operation of the focal plane shutter
The focal plane shutter consists of a rubberized flexible curtain with slits of varying widths that cross the film plane at speeds determined by the tension setting of the spring mechanism. There are 4 slits with widths of 1/8 in, 3/8 in, 3/4 in, 1 1/2 in and “T” (T = “time” setting, used when lens diaphragm shutter is used to control exposure duration. The focal plane shutter is left completely open until manually released. The opening covers the entire area of the film for the size of the camera.) On Speed Graphic models, there are 6 tension settings, adjusted by a butterfly winding knob that increases the speed that the slit crosses the film plane. We send the instructions.