Design

The 24-70mm f/4's design will look instantly familiar to Canon users - it bears a distinct family resemblance to other L series standard zooms, and the EF 24-105mm f/4L IS USM in particular. The zoom ring is placed towards the rear of the barrel, with the manual focus ring at the front. A pair of switches on the left side are used to turn autofocus and image stabilization on or off, and on the right side of the barrel is a zoom lock switch that also gives access to the lens's macro mode. Construction is very much like the 24-105mm f/4 too, including dust- and moisture-resistance.

On the camera

The 24-70mm f/4 is reasonably compact, and just as a good a match to the EOS 5D Mark III (left) as it is to the 6D. Most of the controls are perfectly well-placed for operation with the camera to your eye, although the zoom lock switch's position is perhaps not the best if you need to unlock it quickly. Switching the lens to macro mode also requires you to shift your grip from the usual shooting position.

Size compared to 24-105mm f/4 and 24-70mm f/2.8 II

Here's how the 24-70mm f/4 compares in size to Canon's existing L-series normal zooms - the longer-range EF 24-105mm f/4L IS USM on the left, and the larger-aperture EF 24-70mm f/2.8L II USM on the right. The new lens is the smallest and lightest of the three, but not by all that much. The table below shows how they stack up against each other in terms of vital statistics.

 
24-105mm f/4
24-70mm f/4
24-70mm f/2.8 II
Dimensions
(diameter x length)
 84mm x 107mm
 (3.3 x 4.2 in)
 83mm x 93mm
 (3.3 x 3.7 in)
 89mm x 113mm
 (3.5 x 4.4 in)
Weight  670g (23.6 oz)  600g (21.2 oz)  805g (28.4 oz)
Filter thread  77mm  77mm  82mm
Max magnification  0.23x  0.7x  0.21x

Macro mode

The EF 24-70mm f/4L IS USM has a trick - a special macro mode that allows extra-close focusing, with a pretty impressive maximum magnification of 0.7x. This isn't a new idea by any stretch of the imagination - it was pretty common on manual focus zooms in the 1980s, and Olympus's M.Zuiko Digital ED 12-50mm 1:3.5-6.3 EZ for Micro Four Thirds does something similar - but recently it's been seen much more often on telephoto zooms. Here's how it works.

Macro mode is accessed by pulling the zoom lock/macro switch forward and rotating the zoom ring into the 'Macro' position, marked in yellow. Once in macro mode the zoom ring rotates through the range indicated by the yellow line, which allows composition to be fine-tuned to some extent. The focus range for optimum image quality is marked with a yellow line on the distance scale, but the numbers themselves become invalid, and lens won't focus to infinity.

This all looks great in paper, but in practice things are a little more complicated, because the working distance in macro mode ends up being only about 3cm / 1.2" from the front of the lens to the subject. At this point, you're shooting an image area of about 51mm x 34mm (2" x 1.3") using a lens with a front diameter of 83mm (3.3"), which might make lighting your subject relatively difficult.

On the plus side, Canon has incorporated its 'Hybrid IS' image stabilization system into the lens, as previously seen on the EF 100mm f/2.8L Macro IS USM. This is specifically designed to give improved effectiveness at high magnifications, where most IS systems fail, by detecting and correcting for movement of the lens's entrance pupil relative to the subject, as well as changes in the angle the camera is pointing due to handshake. Canon says the Hybrid IS should give 4 stops benefit during normal shooting, and 2.5 stops for macro work.