Conclusion

The new RF 100-400mm F5.6-8 IS USM is the best super-telephoto lens for most Canon full-frame mirrorless shooters, delivering satisfyingly sharp results and being compact and lightweight enough to carry around all day, and it's also something of a bargain to boot.

The main rival to this lens is the RF 100-500mm F4.5-7.1L IS USM, which at an eye-watering £2899.99 / $2699.99 will be well out of the price range of most people.

For everyone except professional users who will use the 100-500mm day in, day out, at just £699 / $649 the new RF 100-400mm makes a lot more sense from a financial point of view.

Thankfully its not just the price tag that's appealing - it also delivers the goods in most other departments, from image quality to focusing speed, from build quality to feature-set.

The RF 100-400mm offers an extremely versatile focal range whilst being acceptably sharp in both centre and the edges of the frame throughout the focal range, even when shooting wide-open, no mean feat for a super-zoom of this type.

This lens is also capable of capturing some good macro shots when shooting at the 400mm focal length thanks to its maximum magnification of 0.41x.

With the Canon RF 100-400mm F5.6-8 IS USM lens set to its maximum aperture, there is some obvious light fall-off in the corners which you'll need to correct in post-processing. This is much more apparent in the Raw files than the JPEGs. There's also some mild pin-cushion distortion at either end of the focal range but it's not too pronounced.

The other main drawback from an image quality point of view, other than the vignetting, is the quality of the bokeh. With the rather slow maximum apertures on offer, the resulting bokeh isn't as smooth as that from a faster lens, although it's still possible to throw the background completely out of focus when shooting at 400mm/F8.

Used in conjunction with the EOS R6, this is truly a combination that you could carry round all day without really noticing, and without any real compromises in terms of the build quality. Sure, some degree of weather-proofing would have been nice, but given the price, this is hardly a surprising omission.

In terms of features, the RF 100-400mm has a lot to offer for what is after all a non-L-series lens, most notably effective built-in image stabilisation worth up to 6-stops when used with the EOS R5 and EOS R6 cameras.

Auto-focusing proved to be quick, quiet and reliable on the Canon EOS R6 camera body that we tested the lens with thanks to the latest Nano Ultrasonic Motor technology.

Sadly Canon haven't provided either a lens hood or a padded case in the box - both are optional, costly extras - and there's also no tripod collar available for this lens, although it's so light that you arguably don't really need it.

Although we didn't get the chance to try it, the fact that this lens is also compatible with the RF 1.4x and 2x extenders, with no limitations on the zoom range, is a real bonus, although obviously the maximum apertures do become even slower.

Canon have so far mainly focused on releasing super-performing, super-expensive lenses for their EOS R-series mirrorless cameras, so it's great to see such an affordable super-telephoto zoom being released, especially as it delivers much better results and performance than its modest asking price might at first suggest. Highly Recommended!

Ratings (out of 5)
Design	4.5
Features	4
Ease-of-use	4.5
Image quality	4.5
Value for money	5