Table of contents:

What is Shutter-speed?

Shutter-speed is the duration of time for which the film or digital sensor of a camera is exposed to light.

Please have a thorough reading of the page exposure triangle before getting into this page.

Table of contents:

Previously it was stated that there are three important variables for setting exposure in photography, namely, aperture, shutter-speed and ISO. Shutter-speed is one of those three variables to control the overall exposure of a photograph.

In front of the film or digital sensor of a camera, there remains a pair of curtains (named as front curtain & rare curtain) which blocks any light to reach the film or sensor. In general, when we are in front of a scenario to photograph, we first set the composition, framing, focal-length, focus-point, aperture, shutter-speed, iso, white-balance etc. When everything is fixed, we press the shutter-release button which is the final step for recording a photograph.

When we finally press the shutter-release button, one of the curtains folds itself, and allows light to reach the film or sensor through the lens. We skipped a mirror-mechanism in case of DSLRs, which will be discussed in shutter mechanism page. The curtain remains folded for a moment, say for 1500th. of a second, or for ½ or 2 seconds (whatever period we set it earlier). During this period, the film or sensor remains exposed to light, and an image is recorded in digital format. This time period, for which the film or sensor remains open to light, is called shutter-speed of that particular photograph.

The unit of shutter-speed is the unit of time; and may be expressed in seconds, minutes, even in hours.

Imagine yourself inside a very dark room where all the doors and windows are closed. There is day-light present outside the room, but no light inside. Now you open a window just for 1 second, then close it. The room will be exposed to light for 1 second. This time period of 1 second may be called as shutter-speed; and the size of the window may roughy be referred to aperture of a lens.

Different shutter-speeds effect on
1 - exposure of an image
2 - motion of moving elements next page.

Effects of Shutter-speed on Exposure

The overall exposure or brightness of a photograph varies with different shutter-speeds.   Faster the shutter-speed, darker the image, and slower the shutter-speed, brighter the image,   other variables remaining constant.

When the film or sensor remains open for a very less period of time, say for fraction of a second, less light enters the film or sensor, and the image recorded during this period tends to become dark. Such shutter-speeds are called fast shutter-speed.  Examples of fast shutter-speed are 1500th. sec., 12000th. sec. etc. If situation compels you to use a very fast shutter-speed, say to capture a bird in flight, you must compensate light with higher ISO or wider aperture.

varanasi effect of fast shutter-speed

An example of freeze-motion effect with fast-shutter,
f/7.1, 1/4000 sec., ISO 640, 24mm eqv. Varanasi, India 2015
Nikon d810, Tamron 24-70mm f/2.8

Above is an example of fast-shutter ( 14000 sec.) which freezes motion, and tends to darken the photograph.

On the other hand, when the film or sensor remains open for a longer period of time, say ½ or 1 second, more light enters the film or sensor, and the image recorded during this period tends to become very bright. Such shutter-speeds are called slow shutter-speed. Examples of slow shutter-speed are 115, 110, 1, 2 sec...

When the film or sensor remains open for a very long period of time, say for 30 sec., 1 minutes ..., we may call this as long exposure. While shooting long-exposure shots, we must take measures to block the excessive light during this long period of time.

effect of slow shutter-speed

An example of motion-blur effect with slow-shutter, f/4.5, 1/4 sec., ISO 200, 27mm eqv. Katigorah, India 2021, Fuji x-t30, Fuji 18-55mm f/2.8 - 4

The above example uses a slow-shutter ( 14 sec.) and some amount of motion-blur has been captured. Slow-shutter also tends to allow excess light; the above image has been darkened in post-processing purposefully.

Longer the shutter-curtains remain open, more amount of light is allowed to the film/sensor, and the image gets brighter. Shorter this period, less amount of light is allowed, darker the image. The duration for which the film/sensor receives light can be controlled by a switch or from menu of a camera.

The following chart displays the effects of various shutter-speeds and some of their applications.   We must remember that those rules are not rigid, and shutter-speed should be chosen as per the requirement in the field.

Long exposure: ... 1 min... 30 sec...

Very slow-shutter: ... 1 sec... ½ sec...

Slow-shutter: ... 110 sec... 120 sec...

Medium shutter: ... 1125... 1250 sec...

Fast shutter: ... 11000... 12000 sec...

Very fast shutter: 14000... 18000 sec...

Simply, a fast shutter-speed allows less light, and a slow or long shuter-speed allows more light. So, to control the incoming light, we set shutter-speed through the wheels/buttons or the menu of a camera.

shutter-speed 1.6s shutter-speed 0.8s shutter-speed 0.5s

Please observe the above images. The settings of all the three images were kept the same, except shutter-speeds. They were ½, 0.8 and 1.6 seconds respectively. The first image (darkest) has a faster shutter-speed than the second one, which has a faster shutter-speed than the third one(brightest). Thus the brightness of each image varied according to the different shutter-speeds applied.

shutter-speed 1/100s shutter-speed 1/200s shutter-speed 1/400s

Here is one more set where settings of all the three images above are the same; f/11, and iso-64. But shutter-speeds varied as 1400, 1200 and 1100  seconds respectively (faster to slower). Faster shutter darkened the image, while the slower one brightened it.

In case of the first image, because the sensor or film remained open to light for a very small fraction of time(1400 sec), less light was allowed, and the image is the darkest in the series.

Note : It has been observed that a long focal-length requires a faster shutter-speed to avoid recording of any camera-shake. Generally, if you shoot a 300mm shot, set your shutter-speed 1300 sec. or faster.

HDR : High Dynamic Range (Exposure Bracketing)

Why should we shoot the same scenario with different brightness? When a scenario consists of both sky(with bright light) and ground elements, we find the sky to be brighter than the ground. This difference of brightness is most if we aim the camera towards the Sun or a bright light-source. Such a scenario may be referred to as high-contrast scenes. If we meter the exposure from a part of the sky, the resultant image will properly expose the sky, but the ground elements will be under-exposed. On the other hand, if we meter from a part of the ground, the sky will be over-exposed, and the ground will be properly exposed.

The capability of a camera sensor to keep both the brightest and the darkest parts of a scenario properly exposed (to some extent) is known as the high dynamic range or HDR capability of that sensor.

Even if the HDR capability of a camera sensor is very less, we may still get a properly exposed image from a high-contrast scenario by shooting 3 to 5 images with different brightness, and by post-processing them later. Those type of images are known as exposure-bracketed images. Modern cameras have this feature, where you can shoot multiple images with different brightness with a single click of the shutter. A tripod is very helpful in such cases to keep the same frame in all the images.

There are also softwares dedicated to processing of HDR images. They receive a set of bracketed images as input (with different exposures), and produce a single properly exposed image out of the bracketed images. They can also be manually processed to get the output as per personal taste.

Following is an example of a final HDR image generated from three exposure-bracketed images having different exposures. Please use a tripod to keep same frame-alignment for the input images.

HDR : High Dynamic Range (Exposure Bracketing) shutter-speed 10s shutter-speed 2.5s shutter-speed 0.62s   final image

Another example follows, where only two images were merged to produce the final output. Actually, in this case, a single image was almost enough to present without HDR merging, but a slightly brighter-exposure was used additionally to get a bit of details of the land areas.

HDR photography example

An example of a (two) merged image, Camera: Canon g7x mark ii, Badarpurghat, Karimganj, Assam, India 2021.

We have seen how different shutter-speeds affect the exposure or brightness of a photograph. In this page, we shall see how shutter-speed freezes motion of a subject or records motion-blur in a photograph.

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