Photo tip: Preventing blurred photos, without a tripod

24th November 2008
How many times have you composed a stunning shot of a loved one or famous landmark, only to download or print the image to find that camera shake has completely ruined the photo? Don’t worry, not only is it the most common technical mistake people make, it is also very easy to put right. The most complicated part of solving the problem is pronouncing the name of the rule that resolves it - ‘The law of reciprocity’. Reciprocal means a mutual or cooperative exchange and this sums up the solution.

Just bear in mind one thing - this rule works brilliantly, but only if you are photographing a subject that isn’t moving (a person sitting reasonably still is fine).

The solution:
Look at the focal length you are using. If you have an 18-55mm lens and you have the lens set at 55mm (i.e. zoomed right out) you need to ensure that your shutter speed number is at least as high as the focal length. Therefore with a focal length of 55mm you will need to have a shutter speed of at least 1/60th second. For a 300mm lens you would need a shutter speed over 1/300th second. Longer lenses require faster shutter speeds, as any movement of the camera is magnified by the length of the lens. That’s it! As long as you can achieve a shutter speed that is faster than the focal length you are using the photo should be sharp.

So what happens if the fastest shutter speed available is slower than you need with the available light? All you need to do is increase the ISO value. Most cameras, including compact cameras, have a choice of ISO settings. ISO is the digital version of choosing different film speeds. The beauty of digital photography is that you can change the ISO for every shot, whereas film cameras have to finish the film before reloading another film speed.

ISO settings range from 50 to 3200. At 50 you will obtain slower shutter speeds and have maximum image quality. At 3200 you will get the fastest shutter speed your camera can possibly give (with available light), but you will get image ‘noise’. Noise is generally small black dots that can give the image a granular look. In many cases this can detract from the quality of the image, although there are occasions where noise works well – gritty black and white portraits are a good example of where it can work.

If you still can’t get the required shutter speed then you either need to get a tripod, use a flash, or try an image stabilising lens that will allow you to get sharp images at slightly slower shutter speeds.

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