I get asked regularly by my photography students why their images are blurry. The first thing I do is look at the shutter speed and the length of the lens to determine if the blur is induced by camera shake. Usually it is, while the other common cause for blurry images is miss focus.
There is a rule that survives the days when 35 mm film was the predominant photographic medium. It is called ‘The Reciprocal Rule’. It states that you can reasonably expect to hand hold your camera at a shutter speed that is the reciprocal of the lens focal length.
For example if I am shooting with a fifty millimeter lens then I can reasonably expect the majority of my photographs to be sharp when I use a shutter speed of 1/50 of a second or faster. We take the focal length and turn it into a fraction. Two reciprocal numbers multiply together to get one.
50/1 ✖️ 1/50 = 1
You really don’t need to learn the maths, just turn the focal length into your shutter speed.
For a 35 mm lens the reciprocal would be 1/35 of second exposure.
For a 200 mm lens the reciprocal would be 1/200 of a second.
I round it to the nearest shutter speed.
You will still need to hold the camera steady for this to work. Yes, you will need to hold your breath and squeeze the shutter gently.
With practice and excellent technique this can be extended. So that you can use an even slower shutter speed.
Modern cameras have image stabilisation in either the lens, or camera or both. Having it in both works best with some manufacturers claiming a six stop advantage. They do this with miniature gyroscopes that are so sensitive they track the earths movement and for the moment they have reached the theoretical limit of image stabilisation, until they figure out how to use gps tracking to track the movement of the earth.
Having it in the camera seems to work better than having it in the lens.
Despite having image stabilisation I still use the reciprocal rule for the overwhelming majority of my hand held photographs.
Sheley Beach in Albany Western Australia. This place is so beautiful I can’t wait to photograph it over the next three weeks. Photograph and text copyright ©️ Len Metcalf 2018
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