Canon EF 24-105mm f4L design, build and focusing

The Canon EF-S 18-55mm, EF-S 17-85mm and EF 24-105mm lenses are pictured below from left to right in their shortest configurations. Here the lenses measure 66x69mm, 78x92mm and 83x107mm respectively (diameter x length). Zoomed-in, the EF 24-105mm’s barrel extends with one section by 33mm – see photo lower down the page.

Clearly the EF 24-105mm is the biggest of the three lenses pictured here, and the heaviest too at 670g compared to the 475g of the EF-S 17-85mm and the feather-light 190g of the kit zoom.

So the EF 24-105mm is a noticeably bigger and heavier lens than the popular EF-S 17-85mm, and both dwarf the kit lens in size and weight. Like most quality products though, the extra weight of the EF 24-105mm lends it an air of physical confidence which is so far missing from existing EF-S lenses.

Compare it side by side with the EF-S 17-85mm (or even the EF-S 17-55mm) and the EF 24-105mm’s superior build quality makes it feel like a much more serious product. It also sports better protection against the elements with a rubber sealing on the mount.

That said, the EF 24-105mm can look and feel front-heavy when mounted on Canon’s smaller and lighter DSLRs like the 400D / XTi, and is much better balanced on the EOS 40D. As always, we’d recommend trying it in person to see how it looks and feels to you on your own DSLR.

The EF 24-105mm’s optical design consists of 18 elements in 13 groups with both Super UD (ultra low dispersion) and aspherical glass to combat chromatic and spherical aberrations respectively.

It offers a constant f4.0 aperture throughout its zoom range, which makes it a tad slower than the EF-S kit lenses above when zoomed-out, but a little quicker when zoomed-in. A constant aperture is preferred by professionals because the exposure won’t change as you adjust the focal length.

There’s two switches on the side of the barrel for the autofocus and Image Stabiliser. The latter offers on or off, with no specific mode for panning. See the following page for results showing the effectiveness of the stabilisation.

Like most Canon L zoom lenses, the zoom ring is closest to the DSLR body, while the manual focusing ring is positioned towards the end of the barrel. Both are very smooth in operation and again like other L lenses, you can make very fine adjustments without catching. This really comes into its own when using the full-time manual focusing which lets you manually tweak the focusing at any time.

If you’ve only used EF-S models, the mechanical performance of an L model really does feel a world apart. Unlike existing EF-S lenses, the manual focusing ring is also generously proportioned and much more usable.

As you’d expect, the focusing takes place internally with the front section of the lens remaining static – good news for users of polarising filters, although the thread diameter of 77mm means they won’t be cheap. As an L lens, the EF 24-105mm is supplied with lens hood and pouch; annoyingly these remain optional extras on Canon’s non-L models.

In terms of auto-focusing, the EF 24-105mm’s USM motor is quick and quiet, locking onto subjects easily under most conditions. It’s certainly as good as other USM lenses of a similar aperture, but we felt the EF 24-70mm f2.8 and EF-S 17-55mm f2.8 both had a slight edge in very low light due to their brighter apertures. That said, most people won’t have any complaints with the EF 24-105mm’s focusing performance.

On the next page we’ll show examples of the coverage and Image Stabilisation in action.