Canon RF 24mm f1.8 STM review
Written by Gordon Laing
The Canon RF 24mm f1.8 Macro IS STM is a wide-angle prime lens for the EOS R mirrorless system, aimed at landscape, architecture, vlogging and close-up work. Announced in July 2022 alongside the RF 15-30mm zoom, the RF 24mm 1.8. Like all RF lenses, they only work with EOS R cameras and are not compatible with EOS DSLRs or EOS M models.
While a number of RF zooms already include the 24mm focal length, the RF 24 1.8 actually becomes Canon’s first prime lens to deliver this coverage in the native format. Sure you can adapt a wealth of older 24s designed for the EF mount, but this is the first native RF 24 prime from Canon. Interestingly for its first RF 24, Canon’s chosen to pitch it within its more affordable series – or at least sub-1000, leaving an inevitable higher-end L-version for the future. Find out how it measures-up in my video review below, or if you prefer to read a written version of the highlights, keep scrolling!
At the time I made this review, Canon’s EOS R system remains surprisingly low on L-series primes, with only one 50 and two 85s in the double-digit range. In contrast, the RF 24 1.8 becomes the fifth lower-cost prime under 100mm in the series, joining existing 16, 35, 50 and 85 models, although revealingly it is jointly the most expensive in this group.
I think it’s safe to assume Canon’s RF catalogue will eventually offer every focal length you desire in both relatively lower-cost and high-end versions, but in the meantime I do feel the system would be more attractive if Canon opened up the mount to third parties to fill-in the gaps and provide alternatives not just on price but specification.
Anyway, back to the RF 24 1.8 which roughly slots between the RF 16 2.8 and 35 1.8 in coverage and design, being closest of all to the 35 in size and features.
Indeed at 74x63mm and weighing 270g, the RF 24 1.8 is the exact same size as the 35 1.8 and only a few grams lighter.
Both share the same barrel design too with a 52mm filter thread, clicky customisable control ring, smooth free-spinning manual focus ring, metal lens mount, and separate switches for optical stabilisation and manual focus.
Having a dedicated switch for manual and auto focus may sound like a standard feature for a lens, but it’s sometimes absent on the cheapest models, including Canon’s own RF 16 and 50mm STM; both of these force you to enter the menus to select manual focus, which can be frustrating to say the least.
While some EOS R bodies, like the R7, now include their own AF / MF switch, it remains useful to have on the lens and a feature that makes the RF 24 and 35 a step-up over the cheapest RF models. That said, don’t assume any luxury here, as you’re still not getting weather sealing or a lens hood with any of these non-L models.
In terms of optics, the RF 24 1.8 has 11 elements in nine groups, 9 diaphragm blades, optical stabilisation claiming up to five stops of compensation or 6.5 on bodies with IBIS, and a closest focusing distance of 14cm.
Like Canon’s other lower-priced lenses, the focusing is driven by an STM motor which extends the inner barrel a little in use, taking any mounted filter with it for the ride. You’ll hear it if you’re recording with built-in mics.
Here it is focusing between subjects with the aperture wide-open to f1.8, using a Single AF area on the EOS R6 where you can see it’s smooth and confident, albeit not the fastest tool in the box.
Compare the speed to the RF 24-105 STM here at 24mm and you’ll see the zoom lens can focus visibly faster, although it also has a maximum aperture that’s over two stops dimmer so the depth of field isn’t as shallow or challenging.
Here’s the same test with the RF 24 1.8 but for video, again wide-open at f1.8 and filming 4k on the EOS R6. Canon’s AF system effortlessly pulls focus between the subjects here smoothly and confidently. The focusing motor is audible when using in-camera mics though as I’ll demonstrate later.
And now for the RF 24-105 STM at 24mm f4, again showing a similar focus rack between the two bottles that’s smooth and confident. I’ve muted the sound on both these clips as there was background noise, but the zoom’s motors are essentially silent in operation.
In terms of focus breathing, here’s the RF 24 1.8 manually focusing from infinity to the closest distance and back again. As you focus closer, note the change in magnification becomes quite visible.
Compare it to the RF 24-105 STM zoom here at 24mm, again manually focusing from infinity to the closest distance and you’ll see much less change in magnification due to breathing.
But remember the zoom can’t focus as close as the prime here, so if I show them both side by side focusing between the same distance range of infinity to around 20cm and back again, you’ll see their change in magnification is actually roughly similar.
Ok, next for coverage starting with the RF 24 1.8, and to put it in perspective, here’s the RF 16 f2.8 for comparison, before switching back to the 24 and then using the RF 35 1.8 from the same position, and finally back to the 24. Each has its place, but for me 24 is one of my favourite focal lengths, wide enough to grab a big view, but not so wide you have to worry about distortions too much. It’s also perfect for vlogging and product presentation videos.
Like most modern lenses, the RF 24 1.8 employs a profile to compensate for geometric distortion and vignetting. You’ll notice Distortion Correction is greyed-out and always applied for in-camera JPEGs in the menu, so you don’t need to do anything.
If you’re processing RAW files, most converters will also apply the profile by default, but you also have the option to turn it off to see how much is being corrected behind the scenes.
So here’s the coverage again from the 24 1.8 STM with the profile applied, before switching to a version processed without the profile, and as I toggle between them you can see the corrections taking place.
For comparison here’s the RF 16 2.8 STM switching between versions with and without its profile, where you can see the corrections are much more substantial, going beyond a mere stretching of the corners.
But compare them to the RF 35 1.8 STM with and without its profile and you’ll see this lens requires the least correction of the three lenses, although to be fair, it’s also the least wide in coverage.
Since profiles are part of modern lens design, I’m personally at peace with them as they allow designs and performance that were previously impossible or out of reach. And they’re academic for most owners too as they’re generally applied by default, so you don’t need to worry. But in my reviews I do like to see what’s going on! For the rest of this review though, lens corrections have been applied to all photos and videos as this is how the lens is designed to be used.
So let’s start with my distant landscape test, angled so that details run into the corners, allowing us to judge the sharpness across the entire frame. As always I’m presenting results with the lens focused in the middle of the frame as this is how you’d normally shoot a distant scene and judge the flatness of the field.
I shot all these tests using the original EOS R and I’ll start with a closer look at the middle of the frame with the aperture wide-open at f1.8. I’ll introduce crops from the RF 24-105 STM kit zoom for comparison at f4 onwards.
So here’s the RF 24 1.8 with the aperture wide-open where the middle of the frame looks pretty good to me with a decent degree of real life detail. As you close the aperture you will enjoy a boost in contrast and overall crispness, arguably peaking around f4.
This is where I’ll introduce the RF 24-105 on the right, shot moments apart and here also set to 24mm f4. I’d say there’s little to tell them apart at f4, nor closed one stop further to f5.6. So a good result for both lenses here in the middle of the frame.
Now back to the RF 24 1.8 presented alone with the aperture open to f1.8 before heading into the corner. Here you’ll see some softening of ultimate detail along with some darkening due to vignetting. Gradually closing the aperture to f4 sees a mild improvement in sharpness, but mostly a lifting of the vignette.
At this point I can put the 24 result on the left and the 24-105 result on the right, with both lenses set to f4. As this is the maximum aperture for the zoom on the right, it’s not surprising to see more darkening in the corners due to vignetting and the 24 prime on the left is a tad crisper too.
Closing both to f5.6 sees mild improvements with the prime still enjoying a small edge, and there’s still a small gap between them at f8. Note I also reshot both lenses with the focusing area moved into this corner and didn’t measure any noticeable benefit, so both fields are fairly flat.
So the RF 24 1.8 prime is a little sharper than the 24-105 STM zoom in the far corners at the same apertures, but I wouldn’t describe their relative performance in this test as reason to buy one over the other. The real benefits of the RF 24 1.8 over a kit zoom are its brighter aperture and closer focusing.
To illustrate this, let’s start with a portrait shot with the RF 24 1.8 with the aperture wide-open at f1.8, and even from this distance there’s a nice degree of separation from the background.
Taking a closer look shows there’s also plenty of detail around my eyes which the Canon bodies make easy to capture thanks to effective face and eye detection. You can also see how the rendering in the background looks well-behaved in this shot.
24mm is not just ideal for environmental portraiture but also a great focal length for presenting pieces to camera, so long as you don’t get too close. You can see the 24 in action here mounted on an EOS R6 using face and eye detection to track me around the frame.
Now let’s put the 24 at 1.8 on the left and the 24-105 STM at 24mm f4 on the right and you can see the impact of the larger aperture on the prime, allowing much shallower depth-of-field effects and greater separation from the background.
The broad coverage, large aperture and close focusing capabilities of the RF 24 1.8 also make it the perfect lens for product presentation videos.
Here I have the R6 on a table top tripod positioned about 80cm away at one end of a standing desk while I present from the other side. Notice not only how well the R6 is focusing the lens, but also how close the lens can focus to the subject, and if you’re interested, that’s a Sony F717, one of many vintage digital cameras you’ll find on my retro YouTube channel, Dino Bytes.
The presence of optical stabilisation also makes handheld filming easier, especially when used alongside IBIS in the R6 here, although you may hear the focusing motors when recording with built-in mics. To be fair it’s not exactly loud, but it’s not silent either, so best used with off-camera mics or for silent b-roll.
Now let’s take a closer look at the quality of the blurring with my ornament test against some fairly lights, starting wide-open at f1.8 of course. There’s decent-sized bokeh blobs and while there’s some outlining, they manage to minimise the distracting onion-ringing patterns inside.
As the aperture is closed, the blobs begin to lose their elongated cat’s-eye shape and become more rounded, albeit influenced by the shape of the nine-blade diaphragm system.
Here’s the 24 1.8 on the left and the 24-105 STM on the right, both with their apertures closed to f4 where the blobs are similarly-sized, but obviously with the different influences of their aperture systems. At f4, the zoom on the right is at its maximum aperture versus the prime on the left which has already been closed by over two stops.
Open the prime on the left to its maximum aperture of f1.8 and you’ll see the difference that’s possible from the same distance, but this isn’t quite the end of the story as both lenses have additional capabilities.
I shot this test at the closest focusing distance of the 24-105 STM zoom for a direct comparison, but the 24 prime can focus closer, so here it is from its closest focusing distance where at f1.8 you can enjoy very shallow depth of field effects if that’s what you’re after.
But so far I’ve only been comparing the 24-105 at the same 24mm focal length, so in the spirit of flexibility, here’s what you’ll get with the zoom at 105mm. I’ve had to move further back to focus and the aperture has closed to a maximum of f7.1 here, but it shows a different kind of perspective you may prefer.
Sticking on the subject of closeups, Canon describes the RF 24 1.8 as a macro lens, although like the RF 35 1.8 and RF 85 f2, it’s only capable of 50% magnification or 1:2 reproduction. Many closeup enthusiasts prefer to reserve the term macro for 1:1 reproduction or even greater, which in the RF series is currently only offered by the 100mm f2.8L Macro, a much higher-end lens I’ve also reviewed if you’re interested.
But 50% magnification still allows for decent closeups as shown throughout this review and while I’ll share more samples in a moment, I wanted to first photograph a ruler as close as I could focus the lens. Here you can see it’s actually captured 67mm across the ruler which represents a fraction greater than 50% magnification on a full-frame sensor.
It’s a good result for the 24, but to achieve this you’ll need to shoot from just 14cm from the sensor plane which runs the risk of casting shadows on your subject. The RF 35 1.8 is only a little better, delivering 50% magnification from 17cm, but the RF 85 f2 is more practical achieving 50% from a distance of 35cm. Either way, the ability to focus close is a useful addition for the 24 1.8 for stills and video alike.
Before wrapping up, one last result showing the 24 1.8 STM with its aperture closed to the minimum value of f22 where point sources of light are rendered with diffraction spikes. There’s 18 here from the 9-blade system and while they’re not the sharpest spikes around, you can still achieve some nice effects.Check prices on the Canon RF 24mm f1.8 Macro IS STM at B&H, Adorama, WEX UK or Calumet.de. Alternatively get yourself a copy of my In Camera book, an official Cameralabs T-shirt or mug, or treat me to a coffee! Thanks!