The Canon SLR system has long included a light, affordable standard prime lens. The zeitgeist has applied the Nifty Fifty moniker to the concept, and the RF 50mm F1.8 STM ($199.99) is the latest edition, this time for Canon’s full-frame mirrorless camera system. You shouldn’t expect world-class optics, but there’s loads of appeal for entry-level photographers getting started with an EOS RP. Pros shouldn’t discount it, either. It’s not in the same class as the RF 50mm F1.2 L, but it’s a fine choice for hikes, walks about town, or any time you’d prefer a slimmer kit.
Light Enough to Carry Anywhere
The RF 50mm F1.8 is one of the lightest full-frame lenses you’ll find for the system, at just 5.6 ounces. It’s also quite small, coming in at 1.6 by 2.7 inches (HD). A thread is included for 43mm protective and special effects filters. Generally speaking, it’s an easier lens to carry than the big RF 50mm F1.2 L (4.3 by 3.5 inches, 2.1 pounds), and is even a bit slimmer than the RF 35mm F1.8 Macro (2.5 by 2.9 inches, 10.8 ounces).
High-end features like weather protection, silent autofocus, and anti-smudge protection aren’t included, but we don’t expect them on a $200 lens. You do get a control ring, one that can be used for manual focus or as a flexible control ring. An add-on lens hood is available as an accessory, but not included in the box.
The lens barrel includes a toggle switch to change functions, but doesn’t have one to change between auto and manual focus. That means the lens ring won’t do anything if it’s set as a focus control and your camera is set to autofocus—you’ll need to dive into the menu to change the focus mode.
It’s not a bad idea to leave the ring set to control focus most of the time, even if you’re a full-time autofocus photographer, as it can certainly turn by accident, leading to unwanted changes to exposure.
Making deliberate adjustments is a pleasant experience—the ring turns with a little bit of resistance and has a slightly damped response, so you can make minor adjustments without taking extra care. That’s in contrast to the similar control rings Nikon includes in its Z series mirrorless lenses which have been, to date, hypersensitive.
Autofocus is neither instant nor silent. Premium lenses focus internally, moving just a few elements to lock focus. The RF 50mm’s entire optical block moves to and fro to set focus. It slows things down a little bit, and introduces some noise to a soundtrack if you’re recording video instead of making still images.
Will you notice? If you typically use Servo focus, you’ll feel the lens elements move as toward or away from a subject and the adjustments aren’t as precise as some others, a concern for action and burst shooting. For most snapshots and One Shot focus, though, everything is fine. If the lens needs to drive across its entire close focus to distant focus range you can expect a slight lag, about a quarter-second at worst.
The manual focus experience isn’t bad at all. The response does ramp—turn the ring quickly for dramatic shifts in focus, or slower for smaller ones, and that’s a downside for pro videographers who demand repeatable focus racks, but this isn’t a pro video lens. Focus breathing, the effect that changes the angle of view along with focus, is visible, and another mark against this one as a video lens.
It offers a very useful close-up focus capability. Focus is available as close as 11.8 inches, measured from the image sensor, good enough for 1:4 macro magnification at its closest focus. You can get closer with the midrange RF 35mm F1.8 Macro, a slightly upmarket prime that focuses closer to capture subjects at 1:2 life-size.
Image stabilization isn’t included in the RF 50mm, so you’ll need to take care not to push shutter speeds too long when working with a body that doesn’t include a stabilized sensor—so far that’s just the first-gen EOS R and the low-cost EOS RP. With those bodies, you’ll want to set the shutter to 1/60-second at a minimum to eliminate blur caused by hand shake. If you have a steadier hand, 1/30-second is usable.
When paired with a camera with a stabilized image sensor, you’ll be able to make longer handheld exposures. I netted consistently blur-free results at 1/8-second, and was able to push to a half-second with some care (and an occasionally blurry shot) along with the stabilized EOS R5.
In the Lab
I tested the RF 50mm F1.8 STM along with the 45MP EOS R5 and software from Imatest. At wider apertures, the lens shows some softness off-center, but just sneaks into our good performance range in the center (3,000 lines). Even so, you can frame subjects off-center and still use the lens wide open and net good-looking images—but you’ll see a bit less detail when punching in on printing.
Narrowing the f-stop ups resolution, not just at the edges but toward the center. At f/2.8, you’ll net slightly better detail at the center, but edges lift notably, and show almost as much contrast as at the center. You’ll get the sharpest photos at f/4 through f/8. The results at these apertures are excellent from center to edge, around 4,100 lines.
There’s some loss of clarity at f/11 and f/16, but not enough to dissuade you from using them. You’ll net excellent, 14-point sunstars at f/16. The aperture can be set as low as f/22, but resolution drops considerably and sunstars don’t look any better than they do at f/16.
In-camera corrections nip almost imperceptible barrel distortion in the bud. Adobe hasn’t yet added automatic correction for Lightroom editors, but it’s only a matter of time—we’re reviewing the lens soon after its release.
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The camera also brightens corners and edges, which show a natural vignette from f/1.8 through f/2.8. Even with corrections, images show some dimming of corners at f/1.8 and f/2, but it’s not nearly as dramatic as an uncorrected image.
Bokeh is a big reason to buy a bright, prime lens. The RF 50mm F1.8 blurs background naturally, most noticeably at lower f-stops. Defocused highlights are free of any onion ring effect, but aren’t perfectly circular. They take on a cat’s eye shape toward the frame edges at f/1.8 and f/2. The aperture closes down to a more circular shape by f/2.8 and f/4. Blur lessens as you further narrow the aperture, taking on an octagonal shape by f/5.6.
I did note quite a bit of longitudinal chromatic aberration (LoCA) in the bokeh. It takes the form of green and purple color shifts, most noticeable around very bright points of light. If you’re making an image on an icy morning, or taking a macro of condensation on a windshield, it’s prominent enough to be distracting, but you won’t see it in every image.
Better Than Budget
The Canon RF 50mm F1.8 STM makes some sacrifices to meet its aggressive pricing, and for the most part they’re understandable. Its autofocus isn’t the quickest or quietest, but it’s better than similar budget entries for other systems. It’s a very appealing lens for beginners, with a wide aperture for portraiture and low-light imaging, and the level of construction we expect from one of the biggest names in imaging.
We’d love to see Canon add something in between the RF 50mm F1.8 and F1.2 L in focal length, though, as this one falls just a little shy of what serious hobbyists will want in a lens. If you’ve got a critical eye, this is a good fit for days when you want to carry a light kit. The RF 35mm F1.8 IS STM is available now for RF photographers in want of a prime with stronger optics, for around $500, and you have the option of using adapted SLR lenses with one of Canon’s mount adapters.
For now, we’ll recommend the RF 50mm F1.8 STM to any Canon owner searching for a light, low-cost lens. Photographers dipping their toes into the full-frame pool with an EOS RP should appreciate its cost and lightweight build. Shutterbugs and pros will find that it falls a bit shy of top-end results and may want to hold out until Canon adds something a bit more midrange in the 50mm focal length, but have a premium option in the form of the $2,300 RF 50mm F1.2 L USM.
