If we reviewed this lens during the early 2010s - thus before the era of image auto-correction - we'd have rated the Canon RF 24-240mm f/4-6.3 USM IS as ... trash. The resolution, distortion, and vignetting figures obtained from pure RAW files are all catastrophic at the wide end of the zoom range. However, this observation is a bit academic nowadays. This lens was certainly never meant to be used without image auto-correction, and this provides the framework in which we'll have to rate it. Fully corrected, the Canon RF 24-240mm f/4-6.3 USM IS can deliver very decent, maybe even surprisingly good, results. Typical for many lenses of this class, it achieves its best quality in the lower half of the zoom range. The resolution is decent at (the heavily corrected) 24mm setting with a very high center quality and a very respectable sharpness in the outer image field. There is a bit of field curvature, though. The quality is very even across the image field at 50mm and 100mm. Unsurprisingly the quality tanks a bit at 240mm. However, the critical center quality remains very usable, whereas the borders/corners suffer without being poor. If you are using a Canon camera with a 20-26mp sensor, the lens will be plenty sharp at all settings. A curiosity is the difference between 24mm images taken using JPEGs and RAWs (processed via Adobe ACR at least). Auto-corrected RAW files show a bigger field-of-view - which isn't ideal because the viewfinder shows the JPEG version. It's not a major issue but worth noting. The auto-correction didn't fully compensate for the extreme distortions at 24mm, but the remaining barrel distortion is mild and wouldn't bother you in most scenes. At other focal lengths, this is a non-issue. Auto-correction also does an excellent job with respect to vignetting - and that's also very much needed given the native characteristic. While the lens is certainly not aligned to shallow depth-of-field, the technical bokeh is actually pretty good. The same can't be said about sun stars, although let's be honest here - you can't have it all. The biggest optical issue may be a high risk of sub-par centering quality, which is a bit of a disease in this lens class for obvious reasons (the zoom ratio).

The build quality of the lens is surprisingly good. While it doesn't reach professional standards, it feels solid with no wobbling of the inner tubes to speak of, even when fully extended. The lens body is made of decent-quality plastic. One omission related to its target market is the lack of weather sealing. The AF is very snappy, and the image stabilizer is very efficient and dependable.

Given the fact that Canon RF is still a closed system at the time of this review, the Canon RF 24-240mm f/4-6.3 USM IS is the only available super zoom lens available in R-mount - and Canon lets you feel their strategy with its price tag. $1000 for a heavily "underdesigned" lens is quite a toad that you have to swallow. That being said - this isn't unheard of. The Sony FE 24-240mm f/3.5-6.3 OSS isn't any cheaper but quite a bit worse optically. However, in Sony land, you have at least an escape route with the pretty good and reasonably priced Tamron 28-200mm f/2.8-5.6 Di III RXD. Overall, we were positively surprised by the quality of the (auto-corrected) images, so we shouldn't complain too much about it.