We take a closer look at the Canon EF 70-200mm f/4L IS USM and see if it can compete with its f/2.8 sibling
The zoom ring also has a marginally greater throw, making fine adjustments easier in theory though this turned out not to be significant in practice.
Conversely, the focusing ring is rather a long way forward and so is a little difficult to reach without changing grip but, with an AF system as good as this, manual intervention is unlikely to be needed very often (and was not used at all during field testing).
Between the two rings sits a column of four sliders that activate the AF system, change the focusing range, activate the IS system and switch between the two IS modes. Sadly, owing to the same small-diameter barrel that makes zooming easier, the last of these sliders is underneath the barrel and therefore a bit awkward to reach.
There is also a focused-distance window with infrared markings on top of the barrel. If this window had been pushed around the barrel the sliders could have been moved upwards for easier access.
Unlike on the f/2.8 lens, there is no tripod-mounting platform, but that is not a huge issue given the size and balance of the f/4 lens when used with an EOS 50D (or similar) camera body.
Though the f/4 lens has a first-generation IS system (it’s second-generation in the f/2.8 lens) the only obvious difference was very slightly noisier operation. But both lenses were used without problem to photograph at a shooting range, which, like golf, requires near-silent equipment to avoid breaking the competitors‚ concentrations.
Technical testing returned very solid results for all tested focal-lengths across the important mid-range apertures but, as with the f/2.8 zoom, there are clear signs of chromatic aberration at 70mm (but not at other focal lengths).
Overall, the f/4 lens clearly plays second fiddle on paper but it is a very easy lens to carry and to use. Though it is expensive it is only roughly half that of the f/2.8 version, based on Canons SRPs. So there's probably a case for saying Canon has made the f/4 lens too good compared with the f/2.8 version. Its compromises and limitations are slight but its price advantage is substantial.