Shutters

A shutter is a rotating device with a single blade or multiple blades used to interrupt the light source as film is pulled through the gate. The shutter "blanks" the light from the lamphouse as the intermittent pull down motion happens. Shutters also prevent the heat of the lamp from hitting the film plane continuously.

• If the shutter isn't timed properly you will see a travel ghost or ghosting on screen. This happens because the shutter isn't completely blanking the light onto the film plane as the pull down motion of the intermittent occurs.

Types of Shutters

The type of shutter used depends on the type of projector, the application, the pull down speed of the intermittent mechanism, the desired light efficiency, among other variables. Examples of projectors that may use these types of shutters are listed in parentheses.

• single blade (Kinoton, Ernemann, Eastman 25)
• dual blade (Simplex XL)
• dual blade counter-rotating dual shutter (Century JJ, Brenkert)
• 3 blade (often used with variable speed motors)
• 3 blade counter-rotating dual shutter (Century projectors with variable speed)
• 5 blade single (pretty rare, used for studio machines used telecine.

Further reading

• Shutter experiments by Graeme Hogg of Cube Microplex: 1 - 2 - 3 - 4