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Shutter Speed And Long Exposures

by Steph Doran (follow)
Blog (395)      Articles (166)     
Image by Kevin Jaako

Shutter speed is one of the three key factors that make up an exposure; the others being aperture and ISO. It’s not just a tool for regulating the passage of light into the camera; it also has control over motion. By adjusting the camera’s shutter speed, we have the ability to freeze or blur motion. A fast shutter speed will freeze motion, and a slow shutter speed will blur it. While freezing motion is an interesting exercise, this article is about what can be done when using slower shutter speeds.

What is the shutter?

To start with, the shutter is a tiny door inside your camera that remains closed until the shutter button is pressed to take a photo, fully exposing the camera’s sensor to any light that passes through the lens. This is why the button is called the ‘shutter release.’

‘Shutter speed’ refers to the amount of time that the shutter is open, usually measured in fractions of a second. The larger the fraction is, the longer the shutter is open. So for example, ¼ would mean the shutter is open for longer than ⅛.

The camera can also take photographs with exposures of longer than one second. In this case, the number is written without a fraction. On your camera, whole seconds are usually followed by quotation marks (for example, 2” means 2 seconds).

The table below summarises all you need to know about shutter speeds.

For the purpose of blurring motion, any shutter speed where the exposure is longer than 1/60 would be considered a slow shutter speed.

Long Exposures

As mentioned above, using a slow shutter speed will blur any movement in your scene. The slower the shutter speed, the more blurred the image becomes. This can result in some very interesting photos. Here are five scenarios where you can use long exposures to enhance a scene:

1) Capturing Motion

Blurring motion can help to convey abstract ideas, such as speed or activity. A common example of this is capturing a moving vehicle with a little motion blur. Trains, buses and cars can be captured with a slow shutter speed to give the sense that they are flying through the frame. In this case, the amount of motion blur will depend on the camera being stationary, and how quickly the vehicle is moving. In the photo below, the people watching the ride are in focus while the people on the ride are blurred.

Image by Brian Menges

A similar effect occurs when the technique of ‘panning’ is employed. When panning, the camera moves with the subject, tracking its movement. The result is a sharp subject, with a blurred background (opposite to the photo above, where the moving subject is blurred). You’ll often see the technique of panning used in sports and car racing photography. In the case of the photo below, the photographer is on the ride with the subject rather than standing still.

Image by Fraser Speirs

2) Night Photography

At night time, long exposures become necessary, to allow as much light as possible to reach the sensor. You’ll almost always need a tripod at night, as exposure times can be up to a couple of minutes long, depending on your subject and the other camera settings you are using.

Photographing at night is a great opportunity to experiment with artificial light. Balancing ambient light, such as moonlight, in conjunction with streetlights and coloured signs, can create beautiful results.

Image by Brooke Tasovac

Light trails caused by traffic movement are also a popular example of creative long exposure shots that can be taken at night.

Image by Michael Townsend

3) Smooth, Milky Water

Using a long exposure when photographing water can give a scene an artistic or dreamlike quality. Because water is usually moving, using a slow shutter speed will blur it, resulting in a smooth, milky effect. Landscape photographers use this technique to make waterfalls look misty, and oceans look calm. The longer the exposure, the smoother the water, so an exposure could be up to a couple of minutes long.

However, if water is captured during the day, an ND filter would be necessary to compensate for the long amount of time the shutter is open, and prevent the photo from becoming too bright and overexposed.

Image by Nicolas Raymond

4) Painting With Light

You can have a lot of fun with long exposures when you insert your own artificial light, such as a torch or sparklers, into a dark scene, to paint things such as shapes, letters or words. You can even move into the frame to paint in certain areas around another person or subject, and as long as no light hits you and you aren’t standing too still, you won’t be visible in the image.

Image by Luke Wong

5) Star Trails

Star trails in the sky are a popular subject for photographers interested in long exposure techniques. This type of photography requires a lot of patience, as the exposures can range anywhere from ten minutes to multiple hours in length, and you may need to use your BULB setting. When capturing star trails, it’s important to keep your camera steady, and be mindful of any light pollution (such as street lights or electrical lights in high-rise buildings that can be seen in a horizon) that could interfere with your exposure.

Image by Alexan Tremblay

Tools For Long Exposure Photography

Aside from a camera, there are a few tools that are essential for long exposure photography:

A tripod will keep your camera steady. Holding the camera still with an exposure of 1/40 sec or longer is a challenge, so a tripod will ensure you don’t have problems with camera shake.

A shutter release cable or remote is an extension of your shutter button, and allows you to fire the camera without having to touch it (and accidentally knock it). If you don’t have a shutter release, using your camera’s self timer will do just as well. If you find that your images are still looking a little soft, you can also use mirror lock-up to reduce movement inside your camera that can also cause it to shake.

A well charged battery or a battery with a long life is necessary for exposures that last for hours, because depending on the camera, the final image may not be saved if the battery dies before the shutter closes.

An ND filter is indispensable if you want to capture long exposures in daylight, especially on sunny days. ND filters are like sunglasses for your lens, slowing down the amount of time it takes for the light to reach the sensor to record the image. This means that you can use a longer exposure without blowing out your image. ND filters come in various grades of “density” (darkness) ranging between 1 and 8 stops. The darker they are, the more stops the exposure is reduced by.

Why not spend a weekend trying some of these long exposure techniques and seeing the effects you can get? It’s all part of the fun of owning a DSLR camera.

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