Canon RF 100-400mm F/5.6-8 IS USM Lens Review

Canon introduces a potentially extremely useful long telephoto zoom with this 100-400mm f/5.6-8 optic. Where most lenses have rarely extended past 300mm without the price escalating, we have here a much more affordable extension to 400mm, the extra zoom bringing more wildlife and sports subjects into range. This makes it especially interesting, so let's see how the quality holds up, particularly as we zoom to 400mm, coupling the lens with the 20.1 MP Canon R6 full-frame mirrorless body.

Canon RF 100-400mm F5.6-8 IS USM Handling and Features

Weighing in at a very modest 635g and just 164.7mm long, the lens is light and compact, which makes it very easy to handle and carry for long periods of time. There is a bayonet fit for a lens hood, but sadly the hood is not supplied as standard. Arguably it should be, as it would afford protection from flare and also from impact damage to the front of the lens. Hood ET-74B can be purchased separately at £76, not cheap by any means, but the dedicated hoods are always more convenient in use. There is a standard 67mm filter thread.

First up is a slim control ring that has very light click stops and can be programmed via the camera body. It requires a half-press on the shutter release button to activate, a nice touch as that prevents accidental nudging. Default is exposure compensation.

The focusing ring is slightly wider and has a good grip. The action is electronic and utterly smooth. Close focusing depends upon focal length:

The focusing ring is still active when using AF, so full-time manual focus is possible. The Nano USM focusing is virtually silent, very fast and locks on with confidence.

There is full compatibility with the two RF extenders. The 1.4x extender offers 140-560mm f/8-11, with 0.58x magnification. The 2x extender offers 200-800mm f/11-16 with 0.83x magnification.

The wide zoom ring has a very smooth, slick action. It does extend the lens when zooming towards 400mm but the balance is not disturbed. There are clear and accurate markings at 100mm, 135mm, 200mm, 300mm and 400mm.

Finally, closest to the camera body, there are three switches, AF/MF, Stabiliser on/off and a lock to secure the zoom at 100mm. This stops zoom creep whilst carrying, but certainly the lens as new shows no sign of this.

Optical construction is 12 elements in 9 groups, including 1 UD (Ultra Low Dispersion) and 1 Pmo (Plastic Moulded) Aspherical. Canon's SSC (Super Spectra Coating) reduces flare, but there is no Fluorine coating on the front element. Nor is there any dust or moisture resistance, something that would really be very desirable. The diaphragm comprises 9 blades.

As we extend towards 400mm, the inclusion of OIS (Optical Image Stabilisation) is though a really essential feature that seriously extends the usefulness of the lens. OIS on its own is claimed to offer 5.5 stops advantage, and when combined with in-camera stabilisation this increases to 6 stops.

The lens is so light and compact that it is an absolute doddle to use. This brings into range all sorts of wildlife, sports and even portrait and flower photography. Backgrounds can be thrown way out of focus easily. The long focal lengths make portraits of flowers in deep herbaceous borders a breeze. The use of a tripod makes careful composition much easier, and it seems that whether the IS system is on or off makes little difference in this case. Images look equally sharp. Focusing is sharp and accurate.

The only pity is that there are some missing features that would really enhance the package. Dust and moisture resistance is so much more of a necessity as we become used to seeing this feature and enjoying its advantages. A Fluorine coating on the front element would reduce susceptibility to water, dust and grease and this goes hand in hand with the weather resistance. Finally, the proper lens hood would be a major boon.

However, even without these, this is one very efficient, ergonomically well designed and easy to use lens. Let's see if it delivers the goods in terms of quality of results.