In photography, a shutter is a device that allows
light to pass for a determined period of time, for
the purpose of exposing photographic film or a
light-sensitive electronic sensor to light to capture
a permanent image of a scene.
The shutter is the part of the camera that controls
the amount of time the imaging sensor is
exposed to the light coming from the lens. It is
normally closed and only opens momentarily
when the shutter button is pressed. The time it
takes for the shutter to stay open is referred to as
the Shutter Speed and is measured in seconds or
Types of Shutter
There are different types of shutter but the common ones
that are still being used today are the diaphragm shutter (leaf
shutter) and the focal plane shutter.
Focal Plane Shutter
A leaf shutter is a type of camera shutter consisting
of a mechanism with one or more pivoting metal
leaves which normally does not allow light through the
lens onto the film, but which when triggered opens the
shutter by moving the leaves to uncover the lens for
the required time to make an exposure, then shuts.
A diaphragm shutter is a type of leaf shutter
consisting of a number of thin blades which briefly
uncover the camera aperture to make the exposure.
The blades slide over each other in a way which
creates a circular aperture which enlarges as quickly
as possible to uncover the whole lens, stays open for
the required time, then closes in the same way. The
larger the number of blades, the more accurately
circular is the aperture. An odd number of blades is
usually used: 3, 5, or more.
Focal Plane Shutter
A focal plane shutter is so named because it sits
directly in front of the focal plane (i.e., the film) of
the camera. This is an advantage for
interchangeable-lens cameras, because lenses
do not need to have shutters built into them, and
they can be removed and replaced while the
shutter blocks light from the film.
The most common type of focal plane shutter is
the two-curtain type. It uses two fabric curtains
travelling in the same direction across the focal
plane. The first curtain opens across the focal
plane, and after the appropriate delay, the second
curtain closes behind it.
In most focal-plane shutters, the curtains travel at
the same speed regardless of the speed setting:
the shutter speed, the amount of time the film is
exposed, is determined by the delay between the
time the first curtain opens and the time the
second curtain closes.
Cocking the shutter moves the curtains back to
their starting position. Because of the relative
simplicity of this mechanism, it's easy to build
shutters which can work accurately at very high
shutter speeds, up to 1/2000 second.
Modern focal plane shutters may operate either
horizontally, as in the original Leica design, or
vertically, as in the original Contax design. They
may be made of fabric or of light metal sheets.
Shutter lag is the time between pressing the
shutter release and the camera responding by
taking the picture. While this delay was
insignificant on most film cameras and some
digital cameras, it may be a problem when trying
to capture subjects which are moving quickly
such as in sports or other action photography.
A shutter cycle is the process of the shutter
opening, closing, and resetting to where it is
ready to open again. The life-expectancy of a
mechanical shutter is often expressed as a
number of shutter cycles.
In still cameras, the term shutter speed
represents the time that the shutter remains
open when taking a photograph. Along with the
aperture of the lens (also called f-number), it
determines the amount of light that reaches the
film or sensor.
Shutter settings are typically numbers in this kind
of sequence: 2000, 1000, 500, 250, 125 - you
can see the pattern here: each is half of the
previous. Then it goes 60, 30, 15, 8 - kind of half,
or nearly half each time. 4, 2, 1 …
The shutter is a mechanical shade in the back
center of the camera directly in front of the frame
of film you are shooting. When the button on the
camera to take a picture is pressed this shade
opens for a fraction of a second.
If the shutter is open for too little time the
photograph will be too dark. If the shutter is open
for too long the photograph will be too light. Many
cameras allow the photographer to choose a
The advantage of this type of camera is that by
varying the shutter speed the photographer can
control how motion will appear in the finished
1/8000 will stop any motion
1/4000 high enough speed to take pictures while
1/2000 will stop most motion
1/1000 will stop bicyclists and runners
1/500 will freeze a person jumping in the air
1/250 will stop some motion
1/125 to avoid camera shake
Speeds that blur motion. Use a tripod for these
1/60 slight blurring of motion
1/30 very good speed to show a bit of blur when
1/15 the blurring of motion becomes clearly evident
1/8 the blurring motion becomes more pronounced
1/4 the blurring of motion becomes extreme
1/2 high speed motion begins to become invisible
1 medium speed motion begins to become invisible
2 all motion begins to become invisible
4 more motion begins to become invisible
8 motion develops a fog like quality
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