The EF 70-200mm f/4L IS USM features
The optical construction of the lens consists of the lens consists of 16 elements in 12 groups - certainly not a trivial configuration, even for a zoom. This includes a single Super-UD and three aspherical lenses, designed to minimize various forms of aberrations and reduce distortion at wider angles. The build quality of the lens is simply superb, typical of Canon's other L grade lenses, the barrel is made of hardened plastic with nice black finish, fully ruberrized zoom and focus rings, and full sealing against dust and moisture. The lens weighs 670g (23.6oz) and measures 83.5 x 107mm (3.3 x 4.2in), although the lens extends during zooming towards the long end of the supported range, adding extra 3 or 4cm. At this size and weight, EF 24-105mm f/4L IS USM is not the smallest or lightest standard zoom out there, so some users (especially those of you owning a Leica M) might cringe at the idea of using this lens for descrete street photography.
The lens incorporates a modern, USM type auto-focusing motor. Manual focusing is still possible, using a dedicated focusing ring - switch the lens into a fully manual mode using an AF/MF switch found on the side of the barrel, or simply nudge the focusing ring a little bit to correct minor auto-focusing errors. Like with all modern EF/EF-S lenses, Canon EF 24-105mm f/4L IS USM does not have a dedicated aperture ring and all aperture settings have to be controlled directly from the camera. The minimum supported aperture is f/22. As mentioned above, the lens incorporates an image stabilization technology that is marketed to help stabilize the lens up to extra 3 f-stops. This is obviously a nifty feature for hand-held photography. The IS however should be disabled when the lens is used on a tripod - if you don't turn it off, you risk damaging the mechanism, which will keep trying to engage even with the lens positioned completely stationary. And even if you avoid damaging the IS mechanism, you risk additional shake from the internal gyroscopes 'going wild', trying to detect movement. Just swith it off, using an IS ON/OFF switch on the side of the barrel. By the way, the IS does not offer 2nd mode (panning), so it is effective for static scenes only.The lens accepts 77mm screw-in type filters and focuses down to 45cm (1.5ft).
The Canon EF 24-105mm f/4L IS USM was announced in August 2005 as a lightweight standard zoom lens for professionals. Introduced on the same day as the EOS 5D, it's an ideal match for Canon's 'affordable' full frame body, although equally suited to other full-frame bodies including the 1Ds Mark II and 35mm models.
It's also compatible with Canon's other digital SLRs, although models with smaller cropped-frame sensors, such as the 400D / XTi, 450D / XSi and 40D, will effectively deliver a focal length equivalent to 38.4-168mm. In this review we'll test the lens with the 5D, so from this point on will refer to its intended 24-105mm coverage on a full-frame body; if you own a cropped-frame Canon body like the EOS 400D / XTi, 450D / XSi or 40D, check out our seperate review of this lens for these bodies
In this review we'll take an in-depth look at the Canon EF 24-105mm f/4L IS USM lens and compare it against the professional's existing benchmark EF 24-70mm f/2.8L. Is it worth losing a stop for a longer focal range and image stabilisation? Find out here. We'll also compare it against Canon's EF 17-40mm f/4L, which while clearly offering a different range, has become a popular and much more affordable option for the 5D. After all, at around two thirds the internet price of the EF 24-105mm, the EF 17-40mm is one of the cheapest Canon L lenses available.
Superb autofocus
The ring-type USM motor found in the EF 24-105mm f4L IS USM employs ultra-sonic frequency vibrations to drive autofocus with unrivalled speed and near-silent operation. A powerful CPU and improved AF algorithm contribute to speed performance. Good holding torque stops the lens with precision and accuracy, the instant it arrives at the correct focus point and without overshoot. Photographers can choose manual focus instantly and at any time simply by moving the manual focus ring without first having to switch out of autofocus mode.
Constant f4 aperture from 24 to 105mm
The EF 24-105mm f4L IS USM offers the highest possible optical quality with no change in aperture over the full focal range of the lens. This allows photographers to set exposure at the widest aperture and zoom all the way through to 105mm without having to vary the shutter speed. It is the perfect lens for professional photographers looking for a lightweight and extended zoom alternative to its EF 24-70mm f2.8L USM counterpart. The lens employs an almost perfectly circular barrel aperture, helping create attractive, defocused backgrounds.
