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Shutter Speed

Whether electronic in the case of Compact Cameras, or electro-mechanical in the case of DSLRs, all cameras have a shutter. The purpose of the shutter is to allow light to fall on the digital sensor for a specific period of time. This time period is called "Shutter Speed". Shutter speed's main purpose is in contributing to the proper exposure of the photo. A second purpose determines the degree of blur that will occur, if any.

In a Compact Camera, the shutter is opened and closed by turning it on and off; in a DSLR, a mechanical curtain arrangement, not unlike curtains in your house, open and close, thereby controlling the time period that the light will fall on the sensor.

Shutter speeds can vary anywhere from "Bulb" (continuously on) to 1/4000th of a second or less, depending on the camera model. Along with Aperture and ISO, the length of time the shutter is open is part of the exposure triangle that determines the proper exposure. Like Apertures, Shutter speeds use the Inverse Square Law, and have standardized time periods that are spaced so that they are 1 EV (exposure value) apart. Each change in exposure value lets twice the light in, or half the light in, depending if you are increasing or decreasing the speed.
 

Standard 1 EV Scale
Bulb
30s
15s
8s
4s
2s
1s
1/2s
1/4s
1/8s
1/15s
1/30s
1/60s
1/125s
1/250s
1/500s
1/1000s
1/2000s
1/4000s

 

Bulb is a special function that requires the use of a remote, either IR or cable, depending on the camera. The term "bulb" comes from the very early shutter releases that had a squeeze bulb. When you squeezed the bulb, the shutter closed, and remained closed until you released pressure on the bulb. At that point, the shutter would re-open.

With today's cameras, in the Bulb mode, if you use a wired remote, you normally have to keep the button depressed - although some remote releases have a lock that allows it to remain closed without having to keep your thumb on the button. For those cameras with IR remotes, you typically depress the remote once to close the shutter, then depress it again to open the shutter.

On some Nikon cameras, using Bulb mode with a wired remote will result in the display indicating "BULB", and when using the IR remote, the display changes to "TIME" or sometimes "- -".

In most digital cameras, use of Bulb mode is limited to 30 minutes. When the camera shutter is left open and the sensor is active, it generates heat. The 30 minute limit keeps the sensor from generating excessive heat and possible damage.


The effect of Blur

Blur can come from two sources; photographing moving objects, and camera shake, or the inability to hold the camera still. When photographing moving objects, especially those that go across the photograph from left to right (or vice versa) using too slow of a shutter speed can result in the object becoming blurred. This is primarily because the object moves across the screen while the shutter is open. This is typically solved by using a high shutter speed. Shutter speeds in the range of 1/1,000th of a second or less can even stop the illusion of movement of fast moving objects such as helicopter blades.

Sometimes though, the photographer wants to create a sense of movement, and scenes such as waterfalls are typically shot with slow shutter speeds, 1/30th of a second or less, to give the water a blurred or silky smooth look. Panning also can be used effectively to blur the background while keeping the subject in proper focus. Panning is similar to "leading" a target such as shooting a clay-pigeon with a shotgun.

Camera shake is the inability to hold the camera still, and has nothing to do with moving objects. This problem is more of an issue with telephoto lenses as they tend to emphasize the smallest movement. Several techniques can be used to eliminate camera shake; the primary of which is using a fast shutter speed. Other techniques include Vibration Reduction which some lenses and cameras have, as well as use of a tripod.

To minimize Camera Shake, using a tripod, monopod, or Vibration Reduction is recommended for any shutter speeds below 1/60 (or 1/30 if you are really good at holding your camera). For shutter speeds below 1/15th of a second, using a tripod or placing the camera on a stationary object such as a fence post will prevent camera Shake. And even then, the use of a remote (self timer, wired or wireless) is recommended, as simply depressing the shutter can move the camera enough at these slow shutter speeds to blur your photo.

Vibration reduction will reduce blur from camera shake, but it has no effect on reducing blur from a moving object. If using a tripod or other stationary surface, vibration reduction should be turned off. If left on, the vibration reduction can induce blur from the interaction with the tripod or solid surface.

 

Examples

 


Taken at 1/640th of a second, this is a comprimise photo. The propeller blades appear stopped, and it looks like the aircraft will soon fall out of the sky. This is a compromise because if the shutter speed was reduced enough to show motion in the blades, it would result in a blurry aircraft due to it's movement.
 
 

Showing motion with slower moving objects is easier. This was photographed at 1/60th of a second while panning. The cart is sharply in focus while the background gives the sense of motion. Yes, that is Mario Andretti.
 

Shot at 1/320th of a second, this photo stops the action of the water, and you can see individual droplets splashing over the waterfall.
 
 

The same photo - shot at 1/5th of a second - shows the creative use of blur. The waterfall is blurred, and has that characteristic water-veil effect so highly prized in moving water.
 

Another high shutter speed photo, taken at 1/1250th of a second. The blades are not rotating, and there seems to be nothing preventing the helicopter from falling out of the sky.
 
 

Another example of using shutter creatively to show motion is this photo. Here, the background is in focus, but the subject is blurred. This was taken at 1/6sec, and I set the camera atop a fence rail to steady it.
 


Long Exposures

In Bulb mode, or exposures over 1sec, you can use slow shutter speeds for creative effect. The photos below were taken with long exposures, which sometimes require the use of an ND (Neutral Density) filter. Bulb mode is generally not a daylight option, as you cannot normally get the shutter speed slow enough without overexposing the photo. In those situations, the use of a ND filter basically puts "sunglasses" on the lens to allow you to lower the sensitivity further than what the camera is capable of.

 

Examples

 


This photo was exposed for 100 seconds, using a ND400 filter (8 EV reduction). While fireworks photos are normally taken at 20s to 30s exposure times, extending the shutter speed allows multiple fireworks to fill the screen. There are at least 25 bursts in this photo.
 
 

This photo was taken for 1 second in the bright daylight. Again, a ND filter was used to allow a correct exposure to be taken in daylight conditions.
 

This photo was taken for 1/8 second.
 
 

This photo was taken for 1/5 second. Unfortunately, I did not have a tripod, so this was a hand-held shot; but you get the idea.
 
 

One caution with taking slow shutter speed photos. There is a "sweet spot" time wise. Too long of an exposure, even if the exposure is correct, will result in too much smoothing of details such as moving water. But here again, some creative effects can be done. With a ND filter such as a ND400, a 10-20 second photo is possible, even in the daylight. Shutter speeds that slow can completely eliminate any objects that are moving around. So you could take a photo (with a tripod of course), of a city-scene, and all of the people walking around would disappear. Be creative, try different things, and above all - practice.