June 22, 2011
All photography is an abstraction; creating something that looks a bit like the real world, but changed by composition, lens choice and the photographic process. In most cases, the subject of the picture is pretty recognisable, but there are certain camera techniques that can render your subject completely abstract. One of the most effective is to shoot with a super-long exposure that allows your subject to move, making it completely blurred and indistinct.
The first thing to say is that shooting super-long exposures isn’t for everyone, or rather it isn’t for every camera. Many more basic cameras simply can’t do it, and generally speaking, you’ll need a very sophisticated compact or a DSLR to have the level of control and the range of shutter speeds available.
The length of the shutter speed needed will depend on the speed of the subject and also how blurred you want it to be. As a rough guide though, you should look at anything from a few seconds to 30 minutes or more. Obviously, really slow moving subjects such as star trails will need the longest exposure times.
Even sophisticated cameras will only have shutter speeds of up to 30 seconds. For anything greater than this, you’ll need to use a locking remote release and set the camera to the ‘bulb’ setting, which keeps the shutter open for as long as the button is locked down.
You’ll also have to balance the exposure. Each doubling of the shutter speed (for instance from 2 to 4 seconds) lets twice as much light into the camera. To avoid overexposure and your picture being too light, you’ll need to balance this by closing the aperture by an entire stop (for instance from f8 to f11).
The overall exposure can usually be metered using the built-in camera meter, but take a few different versions using different exposures and different shutter speeds to have a range of effects. Naturally, you can assess the results on the LCD screen to check that things are going right.
Sometimes the ambient light will be too bright to allow a slow enough shutter speed to be used without overexposure. In these cases you’ll need to use a Neutral Density (ND) filter to reduce the overall light levels by a given number of stops.
It might sound obvious, but you’ll also need a tripod. Super-long exposures will only work when a part of the picture is kept perfectly still and non-blurred. The longer the exposure, the more stable (and usually heavy) the tripod you’ll need.
Most DSLRs have a ‘Long Exposure Noise Reduction’ mode, which attempts to take out random noise on the picture that results from very long exposures. This creates a much higher quality image, though the downside is a doubling of the effective exposure time.
One of the favourite subjects for creating long-exposure blur is water. It can look a little clichéd, but waterfalls, coasts and rivers can all be shot with a long shutter speed to create an ethereal misty result. This kind of shot is all the more effective when there are rocks or other objects in the water that are perfectly sharp.
If you’re taking night photographs, then moving vehicles – whether it’s the lights from traffic or even flying planes – can be used to fill dark space with long trails of light. The longer the shutter speed the longer and smoother the light trails.
You don’t need great movement to create blur. It’s possible to create star trails at night, with just the rotation of the planet supplying the motion. Depending on the shutter speed this can create vast arcs of star trails.
All images by Steve Davey. Header photo: Malaga by night. A long shutter speed has caused the car headlights to create long trails.
Steve Davey runs a series of photo tours and London courses. See www.bettertravelphotography.com for more details.