Safe shutter speed

A shutter speed fast enough to prevent camera shake during the exposure. Normally, it’s a second divided by the effective focal length of the lens, so for a 60mm lens a shutter speed of 1/60sec should be ‘safe’. The advent of image stabilisers, however, has made it possible to get sharp handheld shots at much slower shutter speeds.

Optical stabiliser

Image stabiliser which moves physical elements within the lens, or the sensor itself, to keep the image steady during the exposure. This is superior to ‘digital stabilizers’ which use image processing techniques to reduce blur, but which also lead to a loss in quality.

Image stabiliser

A mechanism that counteracts camera movement during the exposure. Lens-based stabilisers use a moving lens element, while sensor-based stabilisers move the sensor itself. Image stabilisers are used to get sharper telephoto shots and low-light shots without camera shake.

Camera shake

This is image blur caused by camera movement during the exposure. The longer the exposure (the slower the shutter speed), the more time there is for camera movement to take place. Any movement is also exaggerated with longer focal length lenses (telephotos). There is a simple way to estimate the risk of camera shake – take the effective focal length of the lens and divide it into 1 to get the minimum ‘safe’ shutter speed. So with a 30mm lens, the minimum safe shutter speed would be 1/30sec. However, today’s image stabilisation systems reduce shake and make slower shutter speeds possible.

5-axis stabilisation

The latest kind of image stabilisation technology, where the camera’s sensor can be tilted or shifted on 5 axes to counter a much wider range and types of movement than regular lens-based image stabilisers, and it’s a particular advantage for video, where these additional movements can pose problems during handheld filming. 5-axis stabilisation used in the Pentax K-1 full frame DSLR, Olympus OM-D mirrorless cameras and the latest Sony A7-series compact system cameras.