You may have heard of the Aperture Triangle – I’ll be dealing with that in a day or so. The three sides are Aperture (which we’ve looked at), Shutter Speed (today’s topic) and ISO (tomorrow’s item – probably). ISO and shutter speed are wonderful tools.
Shutter speed refers to how long you leave the aperture open – to let the light from the scene reach the sensor. You’ll have picked up something of that aspect yesterday, I hope. I’ve provided, below, some examples of different types of scene that you may wish to photograph – not to say that you MUST use the speeds shown – but to give you a ball park idea of the order of magnitude that may be involved.
This is a powerboat racing scene, at Carr Mill Dam, St Helens, Merseyside. The boats are moving very quickly. I used a fairly fast speed and ‘panned’, that is, before the boat arrived, I’d already focused on the place on the lake surface where I knew it had to be. I stood still but, with my camera set to continuous focus, I turned my shoulders to allow the camera to track the boat as it passed, firing off a burst of shots at 1/1600 seconds, f/5.6, 260 mm and ISO 400. If I’d used a slower speed, the image of the boat would have been blurred.
I took this photo at a horse race at Haydock Park racecourse, St Helens. Horses don’t move as quickly as racing powerboats, so I was able to use a slightly slower shutter speed and still kept the horses and the background properly focused. I still used the panning technique, focused ahead and used continuous autofocus (AF.C). As the first horse started to move into my frame, I followed it with my camera and fired off a burst at 1/1000 seconds, f/5.6, 85 mm and ISO 400
This shot was my practice session the first time I ever used panning technique. The car is on the M62 motorway in Northern England. I was stood at the edge of woodland. I wanted to create a feeling of speed by letting the background blur. A faster shutter speed would have kept both the car and background in focus – as in the above examples. My ISO of 100 and aperture of f/8 allowed me to use a slower shutter speed to create the effect. 1/30 seconds, f/8, 55 mm and ISO 100.
This is a view of the city of London at daybreak. Nothing is moving apart from the River. I wouldn’t have been able to take this photo with such low light, if I’d used my camera’s minimum ISO of 100 with an aperture as small as f/16. To get the image I used a tripod and let the camera use a quite long shutter speed. 8 seconds, f/16, 28 mm, ISO 100
I shot this view of London from the South Bank of the Thames at night. I still used a narrow aperture for sharpness and a low ISO, but I needed a much longer exposure of 30 seconds to collect enough light at f/18, 30 mm, ISO 100.
Sometimes you need to use a faster shutter speed to compensate for camera shake because you’re not using a tripod. Even with built in image stabilisation it can help. The heavier your camera and lens the more difficult it can be to eliminate camera shake. A frequently quoted suggestion is to set your shutter speed to be no slower than the reciprocal of your focal length. If you are using a 50 mm lens, set your shutter speed to be faster than 1/50th seconds. With a 135 mm lens, shoot faster than 1/135th seconds.
The featured photo today is one that I took just before lockdown, at Trefor Stacks (Ynys Mawr) on the Lyn Peninsula, North Wales. You may have expected that, with the settings below, the whole image would have been vastly over-exposed. Because the the midday sunlight was so bright, I used a 10 stop neutral density filter. I’ll say more about filters in a few days. My settings were 20 seconds f/11, 20 mm and ISO 100. This means that, because my shutter speed, in a test shot, without a filter had been roughly 1/64 seconds at that aperture and ISO, I used a filter dark enough to cut out 10 stops of light. That meant that I could use a shutter speed of 20 seconds to provide an equivalent exposure value.
What do I mean by a stop? A shutter speed of 1/32 seconds is one stop slower than a speed of 1/64 seconds. Two stops would be 1/16 seconds. Keep on doubling the speed ten times from the start and you reach 20. (i.e. 1/64, 1/32, 1/16, 1/8, 1/4, 1/2, 1.25, 2.5, 5, 10, 20) Okay, I did a bit of creative doubling to get from a half to one and a quarter, but I did say roughly 1/64 originally. You can’t be precise with very dark filters because daylight can change from sunny to cloudy in seconds. As I said earlier, I’ll deal with filters again, in more detail soon, when I write about long exposure photography
One last point, on the subject of shutter speed and blur, notice how that 20 seconds exposure has calmed the waves, focusing attention on the detail in the stacks.. You can get some great effects using long exposure. The golden lichen, by the way, really was that bright – no software trickery. I was tempted to make it duller but, what the hell, it was beautiful in my eyes, and it’s my photo, so I left it as it was.
Tomorrow I intend to deal with the third side of the Aperture Triangle – ISO or brightness.