Bryan over at The-Digital-Picture has completed his review of the Canon RF 24-105mm f/4-7.1 IS STM, a lens that will likely become quite popular with Canon EOS R6 buyers when the grab the camera with the lens included.
This is the first f/7.1 lens we've seen from Canon, which may be offputting to some, but for a lot of shooters, it'll be a worthwhile trade-off for the lightweight design and affordable price.
Lightweight, compact, plus very low priced is a formula for mediocre lens image quality at best. Especially with the cost added by the long focal length range and great image stabilization system, incredible image quality was not anticipated. Let's take a look at what the testing shows.
With a wide-open aperture, the center of the frame image quality is reasonable and similar over the entire focal length range. Of course, f/7.1 at the long end is significantly narrower than f/4 at the wide end. Stop down to f/8 at the wide end and … little change is seen. Taking that description to the next level, little change is seen when stopping down at any focal length until the effects of diffraction begin to show.
In general, lenses are not as sharp in the periphery where light rays must be bent more strongly than in the center. This lens' 24mm corners are somewhat soft, but not bad considering the distortion issue that I'll discuss in more depth later in the review. The corners throughout the balance of the range have decent image quality. Stopping down decreases peripheral shading but has little other effects.
Basically, use this lens at any focal length or aperture desired with little bearing on image quality except for the 24mm corners. Read the full review