Canon launched their new RF mount and the first EOS-R cameras in 2018.
The initial offerings consisted of two good but not outstanding cameras, the EOS-R and EOS RP which use recycled sensors from the EOS-5 series and EOS-6 series DSLRs respectively.
At the same time Canon launched some exotic glass which seemed overkill for the bodies.
Clearly Canon had to come up with some budget lenses to match the low cost RP and some high spec bodies to match the exotic lenses.
Both of these requirements have now been addressed in the form of
a) Two consumer-friendly entry-level lenses. These are:
* the subject of this report, the RF24-105mm f4-7.1 IS STM and
* the RF 24-240mm f4-6.3 IS STM.
Hopefully more consumer-friendly small RF primes will emerge in due course, but for now the 24-105 STM is a very good match for the RP.
b) Two high spec bodies, the EOS-R5 and EOS-R6.
RF 24-105 f4-7.1 IS STM
Who’s it for ?
I think this lens is aimed at the camera user making their entry into the RF mount full frame mirrorless system.
The lens is often sold in a kit with the EOS RP body to which it is very well matched.
What’s it for ?
It is a versatile general purpose lens suitable for almost any purpose including close -ups which it does very well. It is not the first lens I would select for low light indoor work but the aperture at 24mm focal length is f4 which is the same as the much more expensive 24-105mm L lens.
Description.
The STM is a compact, light, relatively inexpensive full frame optic.
In fact it is no larger than and is less expensive than many similarly targeted standard zooms for Micro Four Thirds and APSC cameras.
Canon’s strategy here is obvious enough. The EOS RP with bundled 24-105mm STM gets users into full frame mirrorless with a kit which is smaller, lighter and less expensive than several APSC and MFT options.
As an aside I note that Canon’s strategy regarding the relationship between its RF and EF-M models has thus far been consistent. Although the RF 24-105 STM is compact for a full frame lens it is still much larger than the kit 15-45mm zoom for EF-M, although to be fair it also has a greater zoom range.
The STM lens is substantially smaller and lighter and less than half the price of the 24-105mm L lens.
Price* | Length | Diameter | Filter | Mass | |
f4 L | 1410 | 107 | 84 | 77 | 700 |
F4-7.1 STM | 611 | 89 | 77 | 67 | 395 |
* Price (inclusive of 10% GST) on the day I write this at an Australian camera retailer.
No lens hood comes in the box but reversible aftermarket hoods are readily available and modestly priced.
There is one control ring with a slider switch on the lens barrel to select between focus and control.
There is a stabiliser on/off switch also on the lens barrel.
The zoom action is smooth.
How does Canon keep the price point so low ? (compared to the 24-105mm L)
The most obvious way is by restricting the aperture to f7.1 at the long end of the zoom. This is also the main way the size is reduced so much.
But there are others.
Imaging at the wide end relies heavily on software corrections to the very large amounts of barrel distortion and color fringing present in uncorrected Raw files. For this reason Raw shooters need to use a Raw converter such as Adobe Camera Raw or Lightroom or Canon DPP which has correction profiles for this lens enabled.
Even then I find extra correction of distortion and color fringing is often required with some subjects
Lens construction of the STM is 13 elements in 11 groups, 1 aspheric, nil LD, STM focus motor.
The f4 L uses 18 elements in 14 groups, 3 aspherics, 1 UD, air sphere coating, weather resistance and
nano USM.
Lastly the f4L is made in Japan and the STM in Taiwan. Canon is not saying of course but I would not be surprised if quality control at the Japan factory is more tightly monitored than at the Taiwan facility. In recent years Canon has been making its higher spec products in Japan, the lower spec items offshore.
Focus
Autofocus is fast and consistently accurate. Manual focus is easily accomplished on any RF mount body.
Stabiliser
The stabiliser works well with no problems in typical Canon fashion.
Sharpness
On the test chart the lens performs very well at all focal lengths and available apertures with good retention of sharpness to the edges.
However out in the real world things are not quite so good. With some subjects such as sunlit foliage the lens is unable to accurately discriminate fine details towards the edges of the frame. This inability is exacerbated by color fringing at high contrast edges. Closing down the aperture does not help.
By the way this observation reminds us that testing a lens involves quite a bit of work and certainly a lot more than simply pointing it at a test chart under controlled lighting.
Distortion
There is huge barrel distortion at 24mm graduating to mild pincushion at 105mm.
This is associated with high levels of color fringing at the wide end. Both these issues are best managed either by shooting JPG or using a Raw converter with the appropriate lens correction profile.
Flare
The lens is pleasingly resistant to flare from direct or indirect sunlight in or near the image frame. However small details can be obscured by local flare and color fringing as described above.
Summary
The RF 24-105mm f4-7.1 IS STM lens represents an astute move by Canon to entice more users into the world of full frame mirrorless photography.
It is an ideal entry point for someone who does not already have a collection of EF lenses and even for many who do.
It delivers good imaging capability at a very attractive price.
The downsides are the small aperture at the long end of the zoom, high distortion and color fringing (correctable) at the wide end and difficulty rendering fine detail with some subjects such as foliage in strong direct sunlight.
Overall I rate it as recommended with the caveats above.