Focal-Plane Shutters vs. Leaf Shutters

Without a shutter, a camera is just a box.

In the early days of photography, light-sensitive chemistry required minutes of uninterrupted exposure. A lens cap and a stopwatch were enough to control the light volumes. Some modern cameras, including those you can make at home, need no shutter for the same reason: long exposure times. But for the most part, camera shutters will let the light fall onto film for just fractions of a second — not something you can do with a lens cap.

Early cameras had a large variety of shutter mechanisms, though eventually, manufacturers settled on two major designs: focal-plane and leaf (diaphragm).

In this article: How focal-plane shutters work. Focal-plane shutters’ advantages. Focal-plane shutters’ disadvantages. How leaf shutters work. Leaf shutters’ advantages. Leaf shutters’ disadvantages. Choosing your shutter type. Support this blog & get premium features with GOLD memberships!

How focal-plane shutters work.

Focal-plane shutters are a clever mechanism. Their name implies that the shutter is located near the film plane — as opposed to being between the lens elements or in front of the lens. They are generally cheaper to make than leaf shutters, and they can produce much swifter exposure times — up to twelve-thousandth of a second!

But of course, this miraculous exposure speed isn’t promoted by anything as obvious as stronger springs. There’s a trick to it.

✪ Note: Focal-plane shutters are usually implied to be of a rolling-blind design, described below.

Invented in the 1890s, the principle of a plane shutter is a travelling slit behind the lens, close and parallel to the light-sensitive plane.

Leica popularized this design with their dual-curtain system, where the first curtain clears the entire film exposure area at about one-sixtieth of a second, immediately followed by the second curtain — travelling in the same direction. Cocking the shutter would reset the curtains by winding them back — with the gap between the curtains closed.

Shutter speeds slower than one-sixtieth of a second would have the curtains pause in the position of the film plane being completely exposed — for set periods of time.

Shutter speeds faster than one-sixtieth of a second do not increase the actual travel speeds of the curtains. Instead, the size of the slit/gap between the curtains decreases. For example, a slit that’s half the width of the film plane clearing/“scanning” the entire exposure area in one-sixtieth of a second effectively produces a 1/120th of a second exposure.

Faster curtain travel speeds are possible with vertical-travel focal-plane shutters. Designed to look like metal window blinds, they’re made of lightweight, rigid materials that create a horizontal slit. Vertical-travel focal-plane shutters usually move at one-hundred-and-twentieth of a second.