Review by Klaus Schroiff, published August 2010

Introduction

It is the second Canon EF lens to use this technology with the first one being the Canon EF 400mm f/4 USM DO IS. The DO lenses are an own group within the Canon lens hierarchy - they are distinguishable via a green ring at the lens front rather than e.g. the red one used for L class lenses. The DO element is also visually recognizable (unlike UD or CaF₂ elements). You may notice the concentric circles in one of the glass elements in the following image.

The lens has a rather conventional mechanical design - it extends towards the long end of the zoom range. Size-wise it is a fat lens (large diameter) but very short (28% shorter according to Canon) for such a tele photo lens. At 720g it isn't especially light weight but the pretty good build quality, located somewhere between Canon consumer grade and L class lenses, takes its toll here. A negative side effect of the additional weight the zoom mechanism is a rather strong tendency to creep when tilting the lens up- or downwards. Canon has integrated a zoom locking switch but unfortunately this works in the 70mm position only.

Thanks to a ring-type USM drive the AF speed is very fast and basically silent. FTM (full-time manual focusing) is always possible in one-shot AF mode. Unlike most consumer grade lenses the EF 70-300mm f/4.5-5.6 DO USM IS has a non-rotating front element. One key selling factor for this lens is naturally the Image Stabilizer (IS). Camera motion is detected by 2 gyro sensors which measure the angle and speed of the shake. This information is used to shift a lens group off the optical axis (basically a forced decentering) to counteract this motion. The result is a significant improvement of "handholdibility" (3 f-stops equivalent). The IS of the EF 70-300mm DO offers 2 different modes: