Group Test: 24-120mm Extended Standard Zooms

The standard focal length for a camera is one which provides a view similar to that seen with the naked eye: it also corresponds with the diagonal length of the imaging sensor. For full-frame imaging the standard (diagonal) focal length is 43mm, for APS-C and DX sensors it is around 27-28mm and for a Four-Thirds sensor it is 22mm.

All of these focal lengths would be equivalent lenses as far as their field-of-view is concerned and lens manufacturers clearly face a huge challenge when they try to design dual-format lenses that are suitable for use with both full-frame and APS-C sensors as they are trying to satisfy two camps at once. Not only do the sensor sizes differ but also, as a consequence, the range of focal lengths needed to meet a variety of picture-taking situations can be very different.

That being the case, different readers may view two of the four lenses tested here in totally different ways depending on whether the dual-format lenses are to be used on full-frame or APS-C camera bodies (or both). In effect, Canon's and Nikon's lenses change their identity when they are fitted to different camera formats. This same complication does not arise with Sigma's and Olympus's lenses, which are matched solely to APS-C and Four-Thirds sensors respectively.

To complicate matters further, the full-format Canon lens has been tested on an APS-C body (EOS 40D) whereas the full-format Nikkor was tested on a full-format body (D700) so their results will not be directly comparable. This is not necessarily important, however, because neither Canon nor Nikon owners are likely to buy the other brand's lenses!

 Taken using the Nikkor 24-120mm lens with VR enabled to help ensure subject sharpness while also capturing a natural amount of blur on the propellers. The exposure time used was 1/1000sec: a slightly longer exposure time would have been better in this case. Photograph by Jon Tarrant.

See tests of these lenses

• Canon EF 28-135mm f/3.5-5.6 IS Macro USM review
• Nikon AF-S VR Zoom-Nikkor 24-120mm f/3.5-5.6G IF-ED review
• Olympus Zuiko Digital 14-54mm f/2.8-3.5 II review
• Sigma 18-125mm f/3.8-5.6 DC OS HSM review