The Canon RF 100-500mm f/4.5-7.1 USM L IS is another impressive product in the Canon lineup and we expected no less. Within the limits of its aperture range, it is very sharp throughout the zoom range with just a minor drop towards the corners. Diffraction will somewhat limit the potential on high megapixel cameras but this won't be overly noticeable - yet. It's certainly not an issue on an EOS R or R6. The native lateral CAs are very low. Image distortions are absent at 100mm but increase a little towards the long end of the zoom range. There's also some mild vignetting at a fully-open aperture. Lateral CAs/distortions/vignetting can all be auto-corrected, of course, and the related information loss is rather limited given the good raw characteristic. The quality of the bokeh is very good in the lower zoom range but deteriorates beyond 300mm.

Canon is targeting professional users and the mechanical quality is on a correspondingly high level. The used materials are top-notch and the manufacturing precision is superb. That being said, we would have preferred a non-extending zoom mechanism. Canon implemented extensive weather-resistant but we have yet to see a lens with an extending zoom mechanism that doesn't suck in dust over time. That being said - the mechanism has the benefit of providing a fairly compact package relative to the max 500mm focal length. And Canon found some love for this approach with the RF 70-200mm f/2.8 and f/4 USM L IS as well.  

We had some trouble with the AF and IS combined with the EOS R but this has probably been fixed with a firmware update that came in after we finished the test already. Generally, the AF speed is pretty good and Canon's image stabilizer is among the best in the industry. If you own a camera with a built-in image stabilizer, you can also enjoy an extra gain here (+1 f-stop on the R5/R6). If you prefer to shoot from a tripod, you can take advantage of the dedicated (detachable) tripod mount on the lens - and that's also needed for keeping a decent balance in this case.

The Canon RF 100-500mm f/4.5-7.1 USM L IS is a natural choice for Canon R-mount users ... but at this stage, it's also the only native one at the time of this review. Even so - given its capabilities, it's a no-brainer if you can live with its very moderate max aperture. In order to freeze fast action at 500mm f/7.1, you will either need a lot of light and/or boost your ISO settings. Within its scope, we can still rate it as "highly recommended".