Exercise 3.2 – shutter speed and moving water

I have long held the belief that there is no ‘correct’ shutter speed for moving water or, to put it better, there is no such thing as an incorrect speed for moving water. Different shutter speeds simply tell different stories. In this post, I examine a wide range of shutter speeds and also two different types of motion.

The first two sequences are at the Lodore Falls in Borrowdale, running a little empty after a period of dry weather. I therefore worked in close to show a reasonable flow of water and to avoid glare as much as possible.

The first sequence was shot at shutter speeds between 1/640 second and 60 seconds.

At 1/640, my intention was to freeze the motion, for comparison with the slower speeds. Individual water droplets are frozen; there is confusion but I get no sense of motion. At 1/200 and 1/100 it is possible to make out individual droplets together with enough blur to show there is motion and some (admittedly small-scale) violence.

At the intermediate speeds, the movement is  shown by streaks rather than blurred droplets. The one that works best for me is 1/25 s.

The three slowest images were made using an ND10 ‘big stopper’ filter. As the exposure time increases, the details in the moving water smooth out. There is a sense of ‘flow’ in the falling water, the splashes have disappeared or form a light mist, and the froth below the stone takes on a milky appearance, with most of the detail disappearing between 5 and 20 seconds. This area is confused rather than flowing.

The second set of images takes a wider view, with an obvious direction of flow. Shutter speeds were between 1/250s and 60 seconds. A polariser was used to minimise glare by ‘killing’ some reflection from the rocks behind the water. The lower fall and the rock are those seen in the first sequence.

Again, the fastest shutter speed freezes the motion. In this case, there is enough detail to be interesting. However, my preference is for the images between 1/100s and 1/10s, where we see both detail and motion blur and get a feeling of flow and tumult. With the longer times, particularly at 60 secs, there is a feeling of ‘flow’ but the individual droplets are lost and the impression is much more peaceful. The appropriate speed depends on the message one wants to convey. My favourite from this set is the image made at 1/8s.

In the third set, I look at a water surface moving in the form of ripples but with no overall flow. Shutter speeds were between 1/1250s and 60 secs

Tonal differences between the top and bottom row may arise from the use of an ND10 filter for the bottom row. We see individual ripples in all the top row images, with blur starting to intrude at 1/13s. With the two faster images on the bottom row, we know that the surface is rippled but is being smoothed out; I get the best impression of motion a 1.6 secs. In the two longer exposures, the motion has been smoothed out to a ‘frosted glass’ texture. There has also been time for clouds to pass over and their shadows to average-out, so the overall tone is smoother.

I am aware that bigger waves have a longer period and would require correspondingly longer exposures to get a similar effect. The ‘surface’ would also appear more as a layer of mist.

Overall, there appear to be three ‘zones’ of effect arising from shutter speed. Very fast shutters ‘freeze’ the movement and show detail, but can look a bit artificial. Medium shutter speeds (say 1/100s to 1 sec) give the best impression of movement and tumult. The very slow shutter speeds, seconds or minutes, average-out the random fluctuations (thereby appearing more serene) and show the underlying flow or stillness of the body of water.

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