Dustin Abbott says in this review of this lens: “Not particularly sharp at any focal length”.
Since I got the impression that my images with this lens were very sharp, I decided to do some pixel peeping of my own. I also own the RF 24-105mm F4 L IS USM which was used for this comparison.
A book shelf with books was shot as test target with the R5 from a tripod using both lenses at 50mm focal length. The aperture was set to f/5.0 being the largest aperture for the RF 24-240mm at 50mm, ASA setting was 400. Three images were taken with the same settings but with different locations of the AF-point: utmost left, center and utmost right. Its purpose was to verify that the sensor plane was parallel to the plane of the test target.
A crop of 900x1600 pixels was made of the left edge of the image in DPP using the raw images without any sharpening. The images were converted to jpeg for this forum.
Results: center sharpness was the same, even at 200%. But surprisingly the edge sharpness was also the same, even maybe slightly better for the non-L lens. I realise that there is more than sharpness to characterize the qualities of a lens, but still I found this result remarkable. By the way, I also own the RF 50mm f/1.2 which was included in the test and destroys everything else at that focal length but that is what you expect.
RF 24-105mm F4 L IS USM: edge sharpness
RF 24-240mm F4-6.3 IS USM: edge sharpness