Teleconverters – or ‘extenders’ as Canon calls them – give you even more pulling power. These accessories can be fitted between the camera and a compatible lens to increase the focal length. Canon offer 1.4x and 2x extenders in both EF and RF mount fittings. The 1.4x extender increases the focal length by 40 per cent – so a 400mm lens gives you a focal length of 560mm. It costs one stop of light though, so the maximum aperture will be one stop slower (a 400mm f/5.6 lens effectively becoming a 560mm f/8 lens with the extender in place).