The Exposure Triangle – Understanding Shutter Speed

In the last post, I began a 3-part series on The Exposure Triangle. Today’s article addresses the second leg — Shutter Speed.

Understanding Shutter Speed

The previous article discussed the importance of aperture in photography, and this one will explore how shutter speed impacts a picture. Aperture’s key influence is the depth of field in a scene, whereas shutter speed allows a photographer to capture or illustrate motion. If you’re interested in sports and action photography or wonder how to capture the flow of a waterfall in a picture, you need to develop an understanding of shutter speed.

The shutter mechanism in a camera prevents light from reaching the sensor until you press the shutter release button. In traditional film cameras and more advanced digital cameras the shutter is a physical mechanism, but basic models use digital shutters. The end result is the same. Once you press the release button the shutter opens and light exposes an image to a piece of film or a sensor. In other words, the shutter speed is the amount of time that your camera lets light pass to the sensor (or film). Shutter speeds are measured in fractions of a second. Most smartphone cameras and basic digital devices have ranges from around 1/15 of a second to 1/500 of a second. Digital SLR and micro four thirds cameras can shoot at speeds as high as 1/5000 or even 1/8000, making them ideal for serious sports photographers.

One of the common frustrations amateur photographers experience is unexpected blurring in their pictures. This is known as ‘camera shake,’ and is the result of the shutter speed being too slow. Natural movements of the hand mean the images appear out of focus. The focal length has an impact on the slowest shutter speed that can generally provide a blur free image. This is because increasing the focal length not only makes the image larger, it also magnifies the effect of camera shake. For most subjects in normal lighting conditions, shutters speeds of 1/60 and faster are generally safe and should produce sharp pictures. If shooting a moving subject, such as a child dancing, you will need to increase this to 1/200 or higher. A lens with image stabilization or a camera body with built-in stabilization can usually allow you to hand-hold a couple of stops slower, before you need to make the camera more steady, often with a tripod.

The Reciprocal Rule is a basic ‘rule’ of photography that can help you decide on the best handheld shutter speed for a given effective focal length. It says the the slowest shutter speed should not be lower than the reciprocal of the focal length (1/focal length). For example, if you are using a 50mm lens, you can probably hold the camera steady with a shutter speed of 1/50 second, or faster. If you increase the focal length to 200mm, then your shutter speed should be 1/200 second. Notice that I said ‘effective focal length. If you are using a camera with a crop factor or 1.5x, then a 50mm lens is effectively equal to 75mm, so your shutter speed needs to be 1/75 second, or faster. A 200mm lens would have an effective focal length of 300mm, so the shutter speed should be 1/300 sec, of faster.

If you are using a micro four thirds camera, the sensor had a crop factor of 2x, so the effective focal length multiplies by two. However, with built in multi-axis stabilization, in the camera body, many photographers are finding they can hand hold two to five stops slower than they could without in-camera stabilization.

If you’ve ever wondered why landscape photographers often work with a tripod, shutter speed is often the answer. As the previous article explored, landscape photographs generally work best when shot at narrow apertures for maximum depth of field. To maintain the correct exposure, slower shutter speed settings are required. Mounting the camera on a tripod allows the photographer to shoot a scene without fear of camera shake ruining the result.

Sports and action photographers have to be able to freeze the moment to capture pin-sharp images. They typically work using shutter speeds of 1/1000 upwards. Motor sports can be particularly challenging, with vehicles travelling at hundreds of miles an hour. As well as being able to shoot at these fast shutter speeds, sports photographers need cameras capable of shooting several frames a second so they can be sure not to miss the action. Working at fast shutter speeds usually means wider apertures are required, so telephoto lenses with F2.8 lenses are the preference of professional sports photographers.

Instead of freezing action, a photographer sometimes wants to illustrate motion in a picture. One of the most effective examples of this type of shot is a flowing waterfall or the waves crashing on a beach. Shutters speeds of several seconds are required to capture this effect, and the camera must be mounted on a tripod. Objects like rocks and static features will be still, but as water moves during the exposure it takes on a misty quality. Some experimentation in required, and you will need to use your camera in manual mode. A neutral density filter allows you to shoot longer exposures (drag the shutter)in bright conditions.

Most digital cameras don’t offer shutter speeds slower than a second, but they offer a so called ‘bulb mode.’ The name of this feature dates back to the days of film cameras and chemical flashbulbs. When bulb mode is selected the shutter remains open for as long as the shutter release button is pressed. Exposures of twenty or thirty seconds, which are ideal for capturing the movement of the sea, are possible in bulb mode. Remote controls are helpful for reducing the camera shake caused by your finger pressing on the shutter button, at long exposure speeds. If you don’t have a remote control, you can reduce the vibrations caused by your finger by using the camera’s self-timer.

Once the photographer understands how to make very long exposures, pictures of the moon and night sky become possible. Mounting the camera on a tripod is essential for this type of shot. (Some photographers have achieved acceptable hand-held shots with micro four thirds camera with built in multi-axis image stabilization. Choose an area away from streetlights to avoid contamination by man-made lights. Use a self-timer or remote release to avoid making the camera shake when you press the shutter release. A lot of trial and error is required when photographing the night sky, but the results can be amazing.

So far, we have talked about two components of the exposure triangle: Aperture and shutter speed. Next week, we will look at the final leg: Sensitivity (ISO).

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