The relationship between shutter speed and aperture is fundamental to the understanding of exposure and photography on the whole. While the latter primarily controls depth of field, the former can transform images with presence of blurred motion or, at the other extreme, freeze an instant of time by thousandths of second.
The term ‘shutter speed’ refers directly to how long the shutter within your camera remains open, and therefore how much light is able to reach the sensor. Shutter speeds are measured in seconds and fractions of seconds – the longer the shutter remains open at a set aperture, the more light will reach your camera’s sensor, and vice versa.
Shutter Speeds – Which Shutter Speed
Which Shutter Speed
When looking to keep images sharp, a good general rule of thumb is thus – the maximum shutter speed you can use is 1/ your focal length. For example, take a focal length of 50mm – the longest shutter speed from which you can expect a sharp image is 1/50 second. Image stabilisation goes some way to extending this, but it’s best not to rely on this if razor-sharp images are needed.
Should you be looking to produce panning shots with some action-based motion blur, somewhere around 1/15-1/30th will keep enough of the action sharp, yet provide discernible motion blur.
For long exposures, for example when capturing star trails or blurring moving water, a tripod will be required. Anything below 1/30th second won’t retain absolute sharpness and much longer exposure times will be so great that handholding is impossible. Shooting in considerable darkness can take some practice too, as it’s tricky to meter for available light. Trial and error goes a long way.
Then, of course, there’s getting the overall exposure correct. It’s not always possible to use a fast shutter speed due to low-light conditions, as much as a long exposure may become overexposed when there’s too much light. A balance against available aperture can assist in partially accommodating for this, but this adds the consideration of depth of field control too.
1/4000th sec – Freezing motion
If you’re shooting a particularly fast-moving subject, then a faster shutter speed will freeze the subject mid-action. 1/4000 is common for DSLRs, with 1/8000sec speeds available on top-end kit.
1/250th sec – Handheld sharpness
If sharpness is the name of the game then the faster the better, assuming a desireable aperture is being used. In good light and at regular focal lengths, around 1/250sec is a good marker.
1/30th sec – Panning
The art of panning combines a steady hand with an exposure just the right side of sharp. If the subject is steadily panned it will appear relatively sharp, while the motion-blur of the surroundings will add to the scene’s dynamic.
Shutter Speeds – Shooting Modes
A variety of modes allow for shutter speed control. Auto and Program only allow the bare minimum of adjustments, and shutter speed is not one of them. Various scene modes on your camera are likely to alter the shutter speed to suit the subject.
Moving away from these settings to Shutter Priority or Manual modes will provide absolute control over the shutter – within the parameters of correct exposure for the former, and to any exposure time with the latter. One additional benefit of DSLRs, and some advanced compact cameras, is the ability to shoot in Bulb mode – this allows the shutter to remain open for an extended period of time, which is perfect for extremely long exposures.
Most DSLRs feature a dedicated mode dial, with shutter priority being clearly marked as an ‘S’ or ‘Tv’ option. This will differ depending on manufacturer, with the majority opting for ‘Shutter’ (‘S’), but both Canon and Pentax using the ‘Time value’ (‘Tv’) marking. A further ‘TAv’ mode features on Pentax models that allows for control of both the shutter and aperture, with the camera auto-adjusting the ISO sensitivity.
One of the benefits of a DSLR is that it’s possible to shoot in Bulb mode, thus enabling extended exposures well over the common 30 or 60-second maximum duration. Bulb mode enables creative images to be made, such as the motion of star movement taken over several hours. A remote release is useful to start and stop the shot. Also it’s integral not to move the camera in shot, as hours of exposure time would be ruined with a slight knock.
Shutter Speeds – Get Creative
Altering the amount of time your camera’s shutter remains open increases the amount of light reaching the sensor. an extended exposure, when used well, makes creative motion and blurring effects possible.
Long exposures with the camera mounted on a sturdy tripod lend themselves well to capturing motion. This is no better illustrated than when shooting light trails in low light. Exposures slower than around 1/4 of a second, but ideally in excess of a few seconds, allow light motion to be captured. Other creative possibilities include using a torch to ‘paint’ with light or produce ‘light writing’.
Take control of your shutter speed settings and get experimenting.