Editing Speed Graphic (section)

===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.) <ref name="focal"/><ref name=FAQ2/> 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. On Pacemaker Graphic models, there are only 2 settings (high and low).<ref name="focal"/> The combination of the slit width and the spring tension allows for exposure speeds varying from 1/10 to 1/1000 sec.

{|class="wikitable" style="text-align:center"
!Slit width (inches)
| 1/8 || 3/8 || 3/4 || 1 1/2 || T
|-
!Tension 1
| 1/350 sec. || 1/110 sec. || 1/40 sec. || 1/10 sec. || (open)
|-
!Tension 2
| 1/440 sec. || 1/135 sec. || 1/50 sec. || 1/15 sec. || (open)
|-
!Tension 3
| 1/550 sec. || 1/160 sec. || 1/65 sec. || 1/20 sec. || (open)
|-
!Tension 4
| 1/680 sec. || 1/195 sec. || 1/75 sec. || 1/25 sec. || (open)
|-
!Tension 5
| 1/825 sec. || 1/235 sec. || 1/80 sec. || 1/30 sec. || (open)
|-
!Tension 6
| 1/1000 sec. || 1/295 sec. || 1/90 sec. || 1/35 sec. || (open)
|-
|}