Cameras: Types of Shutter
Two distinct types of shutter can be found in cameras – the focal plane type fitted inside 35mm and some roll-film SLR bodies, and the leaf-shutter seen mainly in compacts but also in a number of medium format SLRs. Both types use an identical system of shutter speed numbering, such as 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000 and so on. These are fractions of a second, and each represents a halving of exposure, or a stop.
A focal plane shutter travels across the rectangular aperture of the film gate either horizontally or vertically. There are actually two blinds moving – the first exposes the film and the second conceals it. The interval between their movement determines the duration of the exposure and it can be as brief as 1 /8000 of a second.
Leaf shutters are sited in the lens adjacent to the aperture mechanism and resemble its iris-like construction. The shutter can be operated using either a control ring on the lens or a release sited on the body and mechanically (or electronically) linked to the shutter. This type of shutter is not capable of the high speeds reached by the focal plane type – 1 /500 of a second is usually the maximum – but unlike the focal plane type it offers flash synchronization at all speeds. If the leaf shutter is contained in a lens which is interchangeable, shutter failure calls for the repair of the faulty lens and not the camera body, meaning that you can still carry on taking pictures with an alternative lens.