In this article we investigate some popular creative shooting techniques including panning to capture a sharply-rendered subject against a blurred background; flash blur by combining slow shutter speeds with flash exposures; very long exposures for landscapes, seascapes, and architecture; and using ND filters for blurring exposures to reduce the visibility of moving objects and to add motion blur to subjects.
A popular application for neutral density (ND) filters is to control exposure durations in order to record moving water as a blur.
Panning involves moving the camera in synchrony with the subject to follow a moving subject along its plane of motion. The result is usually a sharp subject set against a background that is blurred by the camera’s motion. Consequently, the secrets of success are to match the speed of the camera tracking with that of the subject and choosing a shutter speed that is slow enough to allow the background to become blurred.
The objective of panning is to capture a sharply-rendered subject against a blurred background. Even in bright conditions, a relatively slow shutter speed (in this case 1/60 second) is required. Slower shutter speeds will be needed for slower-moving subjects.
Nobody can guarantee perfect pans; you need to practice to get a ‘feel’ for different types of subjects. In most cases, the movement will be in a horizontal plane, such as when you’re following a runner, a rider, cyclist or a vehicle. But it could be vertical (a high diver) or diagonal (a skateboard rider), which is often more challenging.
Try using shutter speeds of between 1/20 and 1/30 second, which should produce visible background blurring for subjects moving faster than about 15 km/hour. With slower subjects, you may need to go as low as 1/4 second but the camera should be mounted on a tripod with a panning head. Always start tracking the subject before you press the shutter button and continue tracking after the exposure is completed.
The nearer the subject is to the camera, the faster it will be moving with respect to the camera. So start practicing within the middle distance. Telephoto lenses will bring distant subjects closer ““ but also magnify the speed of their motion with respect to the camera.
An example of a panning shot taken with a fast shutter speed (1/400 second). The use of a long (300mm) telephoto lens on an APS-C DSLR camera enabled the main subject (the bird) to be sharply rendered, while the turbulent ““ and faster-moving ““ wave is slightly unsharp.
Use zone focusing when the subject’s position and direction of movement are predictable. For subjects that move erratically, the servo-driven continuous AF is often a better choice.
2. Flash blur.
Flash blur results from combining slow shutter speeds with flash exposures to ensure parts of the subject are sharp while the remainder is blurred. The actual flash exposures are typically 1/1000 second or less and much shorter than the shutter speed duration, which records the ambient lighting. The main subject(s) must be within the range covered by the emitted light.
An example of flash blur. The hummingbird’s head and body, which are lit by the brief flash exposure, are captured in less than 1/1000 second, while the rapid motion of the bird’s wings are blurred, even though the overall exposure duration is 1/200 second. ( © Gregory Cox.)
Normally, the flash is triggered just after the shutter opens, which is known as front curtain sync. Most cameras include a slow sync setting that allows slower-than-normal shutter speeds to be used with flash to ensure both the subject and its background are adequately illuminated. The Night Portrait and Party Scene pre-sets typically use shutter speeds longer than 1/20 second. Most cameras provide another slow sync flash option: rear curtain sync, which fires the flash at the end of the exposure, just before the shutter closes.
Rear curtain synchronisation fires the flash at the end of the exposure so any movement captured in the exposure before the flash is triggered appears as a faint blur.
With exposures longer than about half a second, rear curtain sync will produce a faint image trail leading up to a sharp, well-lit main subject, whereas front curtain sync will light up the main subject and then acquire the ambient light, which appears as a faint trail in front of the motion. The length of the trail is dictated by how long the shutter remains open. The instant at which the flash fired is shown by the location of the subject at its sharpest.
Rear curtain sync is the best option when panning because subjects are recorded sharply by the very brief flash exposure, while the blur caused by panning follows them. When used with very slow shutter speeds it can produce unnatural-looking blurring.
3. Very long exposures
Very long exposures can be used to impart motion to subject that would normally be considered static. When exposures are longer than about half a second, the camera must be tripod mounted in order to separate the motion blurring from static subjects in the environment.
The most popular genres for this type of long exposure photography are:
Star trails ““ which track the relationship of the starts in the night sky with the rotation of the Earth. Exposures in excess of 30 minutes are required, with the best shots taking a couple of hours.
Landscapes ““ where the objective is to blur moving clouds or waving grass,
Seascapes ““ to soften the water and make it smooth,
Architecture ““ to make people on the street disappear,
People ““ to suggest motion or make crowds of people appear ghostlike.
Very long exposures are required to capture star trails, created by the rotation of the Earth. This example shows a five minute exposure. Much longer exposures are required for longer trails.
When photographing star trails, the objective is to collect light from distant stars that are relatively faint. That means setting up your camera in a place where there is little or no ambient lighting that might interfere with your exposure. If the moon is in the sky, it will influence the exposure so choose a time when the moon is below the horizon and select a night near the new or dying moon. Air pollution and humidity can have adverse effects on the end results.
In the past, the only way to record star trails was with a single, very long exposure, using the self-timer on the camera or a remote controller to trigger the shot, using the Bulb or Time shooting mode. One side effect of long exposures is noise and, although most cameras include long-exposure noise-reduction processing, noise remains a problem in shots taken with this technique. Increasing ISO sensitivity in order to reduce exposure times doesn’t solve the problem since noise increases with increasing sensitivity.
An example of star trails captured with a single long exposure, in this case 45 minutes at f/5.6 using a 10mm lens on an APS-C DSLR camera. The lowest sensitivity (ISO 200) setting was used for the shot, which took an additional 45 minutes to process in the camera, thanks to long-exposure noise reduction processing.
One way around this is to take a series of shorter exposures at intervals and stack them together to obtain the end result. Wide aperture settings allow for shorter exposure times and a better balance between the star trails and the night sky and other elements in the scene.
Use the time-lapse function in the camera to control the sequence, selecting an exposure time that is just long enough to register the stars as bright objects and setting intervals short enough to just separate individual exposures but still record the light as a continuous trail. The duration can be set for several hours.
It’s not uncommon to have several hundred images in a sequence. Combining the images to produce a single star trail image can be done automatically with dedicated software such as ImageStacker and DeepSkyStacker.
The latest Olympus OM-D cameras include a Live Composite mode that makes the entire process easy. It requires an initial test shot to define light levels and details. The actual exposure is calculated from these data. Users can determine the overall length of the exposure and the camera will capture and stack images, saving them in JPEG or ORF.RAW format (or both). The main limit to the overall length of the exposure is the camera’s battery capacity.
Long exposures can also be used to create blurring effects by deliberately moving the camera during a long exposure. In such cases, the objective is to record the patterns produced by moving the camera. The attractiveness of these patterns will be dictated by the colours and brightness levels within the subject and how they interact with the patterns produced by moving the camera.
Subject motion blurring creates an interesting contrast with the fixed structures in this available-light shot taken at 1/5 second.
4.Using ND filters
ND (neutral density) filters are used for exposure control because they reduce the intensity of the light entering the camera. This lets you shoot with a longer exposure time and/or wider lens aperture than would otherwise be possible at the ambient light level. They don’t change the way the camera captures and reproduces colour so they have no effect on the colour balance of images.
But they DO reduce the brightness of the image in optical viewfinders and with strong ND filters, the viewfinder image may appear quite dark. You may need to compose and focus shots before fitting an ND filter to ensure both are correct. This effect doesn’t happen with electronic viewfinders (EVFs) or on monitor screens because the camera compensates automatically and most cameras also provide manual overrides for adjusting screen brightness.
Common applications for ND filters include:
Blurring exposures to be used to reduce the visibility of moving objects.
Adding motion blur to subjects.
Extending the length of time exposures.
ND filters are specified by their light-reducing ability, usually in f-stops (although other designations (e.g. light reduction and density) may be used. The table below lists some common ND filter values along with applications in which these filters are typically used.
As well as regular ND filters, there are also graduated ND filters, which are dark grey at one end and clear at the other, like the tinted windscreen on a car. They are mainly used to balance out the effect of bright skies so foreground details and colours are reproduced with a more natural looking balance.
Variable ND filters are also available. Consisting of two polarisers sandwiched together in a circular frame, they provide continuous adjustments of light transmission as the rotating filter is turned. Most provide between two and eight f-stops of darkening.
An example of the use of deliberate blurring to capture movement in the subject. A 4x neutral density filter was used to allow a shutter speed of 1/10 second to be used with a 300mm lens on an APS-C DSLR camera. Two types of blurring can be seen in this shot, produced by moving the camera combined with subject motion during the exposure.
Excerpt from Action Photography