Canon 17-40mm f/4 L USM

This lens, which has become almost legendary amongst Canon users, has been around for a little while now. There are a number of new or updated contenders on the market in what has been a competitive sector. We look at how this war-horse is standing up.

Specifications

• Focal length 17-40mm
• Aperture f/4
• Angle of view
• Filter size / type 77mm
• Construction Elements/groups 12 elements in 9 groups
• Focusing type Internal USM
• Closest focus 0.28m
• Weight 0.500kg
• Dimensions (Dia x length) 83.5x96.8mm
• Mounts available Canon
• Tripod bush No
• Price (SRP) £ 599.99

Build and Handling
Being designated an L lens almost guarantees that the build quality of this lens will be good to excellent and you will not be disappointed in this area. The design incorporates the usual controls, a zoom ring marked at 17, 20, 24, 28, 35 and 40mm, a distance window with no attempt at a DOF scale, and a well torqued manual focus ring. There is an MF/AF switch to the left of the distance window, and that is about it. During manual focus, the ring requires about a third of a turn from one limit to the other but does not move during autofocus. Autofocus can be manually over-ridden without switching and the whole operation is silent and quick. The lens does not change length during either AF or zooming operations and the front element does not rotate, making the use of filters much simpler. The 77mm filter thread is also a popular size, which, although not small, does help to keep long term costs down. The lens is kept down to a reasonable size considering it was designed for 35mm cameras and can be used on them and full frame digital as well as cropped sensor cameras.

Optical Quality
As mentioned in the opening paragraph, the lens is almost legendary and does produce fine results. But with the ever-increasing resolution of high-end sensors and Canon’s recently stated intention to produce more full frame sensors, can this lens keep up with the game. It is widely recognised as a lens with good contrast and control of distortions and the handling of chromatic aberrations is pretty good also, so more interest during the test procedure was placed on the pure resolving power of the lens. The answer is that, as things stand at present, it is fine. But, and we are talking the top end of the existing cameras here (1Ds MkII at 16.7mp), any more resolution and the lens will start to struggle. With lesser cameras there is not a problem and the lens will easily cope with such megapixel marvels as the newly announced 5D. The fact remains that some of the newer designs, especially those made purely for cropped sensors can out perform this lens from a resolution point of view.

In the confined areas such as street carnivals, the 17-40mm focal length of this lens is an ideal range and one that works on both cropped as well as full frame sensors. Canon 1D (1.3x crop)

The lens is ideal for stock photographers who need to shoot the same scene in different orientations. Shot at 20mm (above) and 30mm (right) from the same spot on the Canon EOS 1D With a relatively fast aperture of f/4, the lens is still useful for low light and unobtrusive indoor photography. 1/60th at f/4 and iso 400. Canon 1D

Click on each comparision photo below to view full size versions

17-40mm set at 17mm and f/8	17-40mm set at 40mm and f/8
17-40mm set at 17mm and f/4	17-40mm set at 40mm and f/4

Below is our lens test data. To find out how to use these graphs look at this article: How we test lenses

Verdict
This is an exceptionally good lens and deserves it reputation, finding its place in most camera bags of professionals using Canon gear. The slightly warm colours produced by Canon L glass and the good contrast and control of other elements required for a nice lens are all there. The results will not disappoint. With recent improvements in lens design however, at the very top end it is staring to look a little long in the tooth.

In summary, the main positive points of the Canon 17-40mm f/4 L USM lens are:
Consistent performance throughout the focal range.
Build quality.
Good value for money

Negative points are:
Top end cameras already at the limit of this lens’ resolution.
Edges drop off a bit as focal length increases.

Check the latest price of the Canon 17-40mm f/4 L USM here

Test by Ian Andrews www.wildaboutkent.co.uk

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