Introduction
Canon’s new R system is still at the very beginning of its journey. However, it starts with two standard zoom lenses. One of them, the Canon RF 28-70mm f/2 USM L is out of reach for most mortals thanks to a sky-high price tag, while the other one, the Canon RF 24-105mm f/4 USM L IS, reviewed here, will surely find its way into the bag of most EOS R owners. It’s worth noting that Canon is bolder than Nikon with their 24-70mm f/4 for the new Nikon Z system – and most users will probably appreciate the extra flexibility as well as the fact that it’s barely more expensive at “just” 1100USD/1200EUR. Depending on the specific market, it may be a little more affordable when purchasing it as part of a camera kit. Interestingly, the price is identical to the Canon EF 24-105mm f/4 USM L IS II (for DSLRs). Let’s hope that this is a glimpse of hope for the lenses to come because other mirrorless camera manufacturers have been pushing lens prices way beyond what we’ve seen in the DSLR segment.
In terms of construction, the RF 24-105mm f/4 USM L IS follows the recent “light-weight” Canon L design philosophy introduced with the Canon EF 85mm f/1.4 USM L IS. This design may not feel as “dense” as on Canon L lenses of old, but we’d easily rate this as very good and up to professional standards. It also features weather-sealing. The lens does, however, extend when zooming towards longer focal lengths. The zoom and focus control rings operate smoothly. Just like on the RF 50mm f/1.2 USM L, you will find an additional control ring at the lens’ front. It can be used to adjust a variety of settings, including aperture, ISO, and exposure compensation. You can also lock the lens in transport position, albeit we didn’t experience any zoom creeping during our time with this lens. A petal-shaped lens hood is provided.
The AF system uses Canon’s “Nano USM,” and we have been a big fan of this one ever since we tested the EF 70-300mm f/4-5.6 USM IS II. It’s very fast, even by DSLR standards, and silent, too. Manual focusing works by wire, and it’s best in class as far as precision goes. The RF 24-105mm f/4 USM L IS is a comparatively slow lens, but this is at least partially offset by an optical image stabilizer. Canon claims that it provides a gain equivalent to 5 f-stops. We wouldn’t sign that statement with blood. In silent shooting mode (electronic shutter), we got around 3.5 to max 4 f-stops from it, which is still good, of course.
| Specifications | |
|---|---|
| Optical construction | 18 elements in 14 groups including 1xUD, 3x aspherical elements |
| Number of aperture blades | 9 (rounded) |
| min. focus distance | 0.45m (max. magnification ratio 1:4.16) |
| Dimensions | 83.5×107.3㎜ |
| Weight | 700g |
| Filter size | 77mm |
| Hood | petal-shaped (bayonet mount, supplied) |
| Other features | weather-sealing, image stabilizer (5 f-stops), front control ring, fluorine coating |
Distortion
Most mirrorless camera manufacturers (Hello Sony, Panasonic, Olympus, Fuji) rely on image auto-correction thus, they are under-designing their lenses. To some degree, this can make sense if minimizing size/weight is the goal (or profits …). This is only our 2nd RF lens review, but so far, it seems as if Canon does not share this philosophy – which is a good thing in our book. The Canon RF 24-105mm f/4 USM L IS does have its share of image distortions, but they aren’t quite as extreme as what we’ve seen elsewhere. At 24mm there is, of course, a fairly heavy degree (3.3%) of barrel distortion, but it’s still within acceptable limits. At the other focal lengths that we tested, there are slight to medium pincushion distortions. If this is too much, you can, of course, still activate image auto-correction to handle these issues.
Vignetting
The vignetting characteristic is a bit higher than on the (DSLR-centric) EF 24-105mm f/4 USM L IS II, but it’s not excessive, and it’s much better than on the Sony FE 24-105mm f/4 G OSS. At 24mm & 105mm @ f/4, you will have to live with a heavy light-falloff of 2.6EV (f-stops) and 2.1EV, respectively. It’s a bit less in the middle range at this aperture. Stopping down to f/5.6 helps a lot in the medium to upper focal length range. At 24mm, you may wish to stop down to f/8 if needed.
If you don’t want to care and activate auto-correction, the issue will be eased quite a bit, of course. The vignetting will stay below 1 EV (f-stop) even at 24mm f/4 – at cost of increased corner noise due to signal amplification.
MTF (resolution)
The Canon RF 24-105mm f/4 USM L IS does a very good job when it comes to image resolution. The sweet spot is at 24mm, where it is capable of producing a very sharp image across the entire image frame, and that’s straight from f/4. There is not much in it by stopping down to f/5.6 (other than increasing the depth-of-field, of course). There’s a marginal loss in corner quality at the 40mm and 70mm settings, but the quality is still very good. The 105mm setting shows a more pronounced drop in border/corner quality at f/4, but it’s not too bad (=good). It is, however, impressive that the broader center zone remains tack sharp – typically, there’s a loss in quality at this setting. Stopping down to f/5.6 lifts the border resolution, but for the best results, you should stick to f/8. A noticeable drop in quality due to diffraction starts to kick in at f/11, but even f/16 remains usable – at least on the 30mp sensor of the EOS R (diffraction effects would be more obvious on higher megapixel sensors).
The centering quality of the tested sample was Okayish, with an irregularity on the right side. The field curvature is comparatively low.
Please note that the MTF results are not directly comparable across the different systems!
Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure of sharpness. If you want to know more about the MTF50 figures, you may check out the corresponding Imatest Explanations
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Chromatic Aberrations (CAs)
Modern, professional-grade lenses tend to have very low CAs. Unfortunately, this isn’t quite true for the RF 24-105mm f/4 USM L IS. While not terrible, CAs can be clearly visible (unless you correct them, of course). That’s especially true for the wide-end of the zoom range, where the averaged CA pixel width can exceed 2px at the image borders (and more so in the corners). Stopping down reduces the issue to some degree.
Just to give you an idea – below is a crop taken from a lab image at 24mm f/4.
Bokeh
Let’s be honest – you won’t (shouldn’t) buy this lens for its shallow depth-of-field capabilities – a max. aperture of f/4 is just not ideal for this purpose. However, if you chose a fairly close focus distance, it’s not an alien concept for this lens either.
One of the typical shortcomings of standard zoom lenses is a somewhat busy rendering of out-of-focus highlights. That also applies to the Canon lens as you can see below. The highlight discs may be circular thanks to 9 aperture blades, but the inner zone of the discs is somewhat busy (onion-style) – probably a side effect of the 3 aspherical elements in the design. The discs deteriorate to cat eyes towards the corners (as usual).
When looking at the general quality of the blur in the focus transition zone, the quality of the bokeh isn’t overly brilliant. The background blur is fairly smooth but not really symmetrical and somewhat smeared. The foreground blur is rather rough with distinctive double-lined edges (Nisen bokeh).
Sample Images
Competition
As of the time of this review there is, of course, no real competition within the EOS R system. Third-party manufacturers have yet to come up with their interpretation of the various lens classes. However, it makes sense to look a little beyond EOS R. As already hinted in the introduction, the EF 24-105mm f/4 USM L IS II is Canon’s offering for DSLRs. While it seems almost identical on paper, it’s not in the same performance league, which supports the argument that the large mount diameter, as well as the closest distance of the rear element to the sensor, can make a difference. A more natural competitor is available over at Sony – the FE 24-105mm f/4 G OSS. The Sony lens is more expensive. Quality-wise it’s hard to compare the two because we tested the Sony lens on a 42mp sensor compared to just 30mp on the EOS R. The Canon lens should have an edge, though.
Visual comparison courtesy of camerasize.com.
The Canon RF 24-105mm f/4 USM L IS is a natural choice for EOS R users - at this point in time anyway. Just like other standard zoom lenses, it has its flaws, but it is clearly one of the better, if not the best lens in this specific class. Canon emphasized the performance at the wide end of the range with an evenly high - in fact, very high - sharpness across the image field. The broader center quality remains excellent at other focal lengths, whereas the outer image region deteriorates slightly. You probably won't notice that in real life at 40mm and 70mm, though. At 105mm f/4, the corners soften a bit more but stay within "good" limits (just) and stopping down helps to overcome this little weakness. Lateral CAs are a little high for a modern lens, but that's easily corrected either in-camera or via a RAW converter. The amount of vignetting is clearly visible at f/4, especially at 24mm, but that's rather typical in this lens class. Image distortions are always present and most pronounced at 24mm. However, we've seen a lot worse in other lenses for mirrorless cameras. The most obvious weakness is probably the quality of the bokeh, but standard zoom lenses are almost never good in this respect.
The build quality is very high, but then we expected no less from a Canon L class lens. Some may think that the used materials are inferior, but that's probably more related to the reduced weight rather than objective criteria.
Conversely, we do certainly appreciate a more lightweight approach compared to similar DSLR offerings. The Nano USM AF continues to impress - it's both very fast and silent, and it can let you forget about your old DSLR combo. Canon's image stabilizer is proven tech by now. Whether you can really achieve the claimed efficiency of 5 f-stops may depend on your personal saturation with coffee, but we didn't reach that in real life. However, it's very good nonetheless.
There is certainly still some potential for improvements. However, standard zoom lenses are very difficult beasts, but Canon did a great job here.
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Optical Quality (30mp)
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Build Quality
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Price / Performance