I'd like to start with a bold statement: “photographs do not record reality accurately; they represent a perception of reality based on the expressive creativity of the photographer who made the image”.
Taking a photograph of the ocean waves pounding a rocky shoreline in bright light at 1/500th of a second freezes the action, allowing every drop of spray to be seen and appreciated. However, this is not 'real'. Feeding our brain a sequence of thirty or so such images per second is much closer to the way we experience reality.
Conversely, the same scene taken in low light, or with a strong ND filter attached to the lens, creates a scene of ethereal mist, abstracting and mystifying the landscape. Again, this is not reality, but the viewer is being shown our intent: power in the first image and mystery in the second.
The choice of different shutter speeds for expressive aims introduces the purpose of this article, which is to show the way to achieve creativity with longer exposure times, and how to visualise things that are not there in reality.
For those familiar with my writing and philosophy, it will come as no surprise that I believe images should contain a strong degree of INTENT from the photographer. Only you were there to witness the event, and the viewer relies totally upon your interpretation of the scene in order to be transported emotionally into the picture. This is a tall order and requires skill, discipline and creativity.
Landscape photography is allowed to extend beyond the boundaries of the literal. We can be expressive, using abstraction or exaggeration, by simplifying the scene, or by rendering its tones in monochrome. Regardless of which techniques we employ, often we are showing personal interpretations of reality in our images rather than completely true to life photographs.
I started this article with a comparison between a fast shutter speed that works well to express energy, and a slow shutter speed that abstracts the motion and creates more mysterious, emotional images. The choice between these two is determined by your intention and what you want to say about a particular scene, but only three creative variables can be adjusted within the given exposure range:
ISO, Aperture, and Shutter Speed
Of the three, I believe shutter speed (TV or S) is the best one for expressing emotions, because we can imply motion and it is our tool of choice when we want to express ourselves and to help our viewers along the road to a position of empathy, helping them to walk a mile in our shoes. Aperture has more to do with depth and ISO deals primarily with the abundance or limitations of available light.
As the sun sinks below the horizon we enter a period of twilight, the time between day and night, which some people call the 'blue hour', as many images taken at this time display a very cool palette. Conditions change gradually but dramatically the moment the sun sets, from scenes that can contain a greater dynamic range than a single unfiltered frame will capture, through to near nocturnal images at astronomical dark, the time when the sun no longer has any influence on the atmosphere.
Naturally, shutter speeds slow down as twilight progresses and the easiest way to create mysterious images is to take them during mysterious light. A shutter speed of 0.6 of a second is perfect for capturing enough detail in moving water to imply motion without destroying its structure. As the shutter speed stretches to seconds and on into minutes, the majority of the structure will be lost, leaving the more graphic flow to represent the motion.
Before moving on to the more thought-provoking element of this article, 'Seeing the Unseen', I need to touch on daytime techniques.
Neutral Density Filters (ND), unlike Graduated Neutral Density Filters (GND), have a solid tint across their whole surface, rather than a gradient that reduces the density from top to bottom. They are available at different strengths, from the standard 1, 2 or 3 stops (0.3, 0.6 & 0.9), up to the latest additions of 6, 10 and 15-stop (square) ND Filters.
Shutter speeds, like apertures and ISOs are measured in stops; adding a 1-stop ND filter to an exposure, where the shutter speed suggested by the camera was 1 second, will require a shutter speed of 2 seconds to give the same exposure.
A 3-stop filter in the above case would extend the shutter speed by 3 stops, 1 second becomes 8 seconds. 1 x 2 = 2, 2 x 2 = 4, 4 x 2 = 8 seconds (where x 2 equals one stop).
Filters of these strengths are used normally when shooting waterfalls or bodies of water such as oceans and lakes. Extending a shutter speed from 1 second to 8 seconds will go a long way towards creating a more abstracted look to the image.
It should be obvious that when using these filters, the shutter speed already has to be quite slow. Taking a picture during the day and trying to reduce the 1/500 shutter speed by 3-stops (1/60) will not blur any motion dramatically. However, this is where the 10-stop ND filter comes into play, when even in broad daylight shutter speeds can be reduced to levels where good degrees of motion can be implied. Even at a starting point of 1/500 shutter speed, the 10-stop ND filter allows a 2 second shutter speed exposure.
1/500 – 1/250 – 1/125 – 1/60 – 1/30 – 1/15 – 1/8 – ¼ - ½ - 1 – 2 seconds
These 6-stop and 10-stop filters are supplied with a chart of recommended shutter speeds that help greatly during long exposures. The final exposure time suggested by the camera needs to be checked before switching the camera to 'bulb' mode and applying the recommended shutter speed, while at the same time choosing the same aperture that was set in the initial reading. A shutter release cable will be required at this stage.
When using these very dark filters, it is important to keep one thing in mind. Once the filter is in place nothing can be seen through the viewfinder: all adjustments (composition, focusing) should be applied prior to inserting the filter into the holder. One last thing to remember is that some of these filters have a tendency to create a slight blue cast on the final image. However, this can be corrected easily in post processing if shooting in RAW mode.
Images taken under bright sunlit conditions, but abstracted with one of these filters, can display a superb dreamy effect. But again, I come back always to the intention, plus an element of visualisation, and it takes a keen eye to recognise situations where the use of ND filters will produce an appropriate image.
Seeing the Unseen
Visualising the effects of long exposures is a skill to be honed, along with many others, allowing thoughtful photographers to create mysterious, dramatic and expressive images from more mundane scenarios than, perhaps, the average photographer can manage.
The latitude of error is huge, however, and as long as the image is exposed correctly, there is little visual difference from a scene taken at 15 seconds or 30 seconds. The skill becomes critical though when dealing with elements within the frame that are unseen at the time, but become very much seen when the image is finished.
Star Trails as Subjects
The characteristic of stars apparently rotating about the poles as the earth rotates is a common enough visual phenomenon for any landscape photographer. Viewers can be moved easily by seeing concentric circles of star trails that create a visual vortex. The effect is predictable, with longer exposures creating longer trails, but it is the mark of a thinker if the visual weight and position of the trails compliments and enhances the rest of the composition.
Star trails are a very dominant subject and it takes a great deal of skill to juxtapose them against terrestrial subjects in a balanced way. It is all too easy to spot scenarios where the position of the trails in relation to the rest of the scene is entirely arbitrary, without awareness, forethought or visualisation.
Consider this: how much care and attention do landscape photographers put into the placement of the subjects in their frames, aligning rocks and trees, mountaintops and sea stacks?
This is a hard enough skill to master with subjects we can see; when it comes to 'Seeing the Unseen', we have to compose for significant visual subjects that we cannot see, but have to imagine, visualise and arrange based on our understanding of how the stars will move throughout the duration of a long exposure.
Thankfully, blessed as we are to be living in the 21st century, all this information is available freely and the passage of the stars across the night sky is predictable to minute degrees.
Latitude & Direction
These are the two most significant variables in any nocturnal composition. Is the camera facing north, south, east or west (or any of the various compass points in between) and what is the latitude?
Polaris, or the North Star will be directly overhead at the North Pole, an elevation of 90 degrees. On the equator, it will lie on the horizon at an elevation of zero degrees. The latitude north or south of the equator can be measured by the degrees of elevation of the pole in the sky. At 55N, the North Star will be 55 degrees up in the night sky.
The stars appear to rotate about both poles and facing east or west, trails can be seen rotating in two directions, with the more dominant rotation in the hemisphere in which you are located.
Creative use of shutter speeds opens doors to expression and creativity that can breathe life and vitality into otherwise sterile compositions. Motion implies emotion, and whether the movement of clouds, rivers, waves, foliage or stars is used, the point is that something unseen is being injected into our images.
To elevate from the norm and the mundane surely must be a challenge to which we should all rise; the landscape around us is a fluid and dynamic organism, full of life, motion and change, and static images frozen in time will rarely capture that energy, life and vitality.
Long exposures, either a product of reduced available light or artificially restricted through the use of ND filters, abstract reality. Part of our expressive toolbox should be to master time and the art of visual expression.