Review by Klaus Schroiff, published March 2015

Introduction

The comparatively big EF 24-105mm f/3.5-5.6 STM IS has a pretty good build quality - not quite L class but not quite on the usual kit lens level either. The lens body is made of high quality plastics based on a metal mount. The lens extends significantly towards the 105mm setting but even so the inner lens tube remains tight. That being said the lens is a bit prone to zoom creeping which is probably why Canon incorporated a transport lock. The rubberized zoom ring operates smoothly. A lens hood is, unfortunately, not part of the package albeit at least optionally available.

Canon's new STM ("Stepping motor") is optimized for silent and smooth operations and as such it is also usable for movies (to a certain degree). The AF isn't as fast as Canon's ring-type USM drive but it is quite snappy and noiseless. The focus accuracy of the tested sample was good. STM works "by wire" so you actually drive the focus motor by turning the (very smooth) focus ring. However, this is hardly noticeable and certainly one of the better implementations out there. Similar to ring-type USM lenses, full-time manual focusing remains possible. Canon also implemented an image stabilizer with a claimed efficiency of up to 4 f-stops (expect less than that if you enjoy your coffee) - which is actually better than on its L-class counterpart.

Below is a paper-spec level comparison to the Canon EF 24-105mm f/4 uSM L IS which is probably the most obvious reference lens for Canon users in this specific class.