We Review the Canon RF 28mm f/2.8 STM Lens

Canon sent me the RF 28mm f/2.8 STM for a review. To be honest, I didn’t expect much from this small pancake lens. However, it grew on me, and I enjoyed using it more than I would like to admit. It has only one downside, and that is its size.

The Canon RF 28mm f/2.8 STM is the next in line for a growing collection of small prime lenses. We tend to keep an eye on the Canon L lenses for the RF mount, which deliver amazing quality, but are large, heavy, and expensive. It's easy to lose sight of the smaller and more affordable lenses.

These smaller lenses also deliver good quality, more than sufficient for most purposes. There is a trade-off, though, like the lack of weather resistance and the use of cheaper materials. In the end, it's the image quality that counts.

About the Focal Length

At first, I wondered about the somewhat odd choice of focal length. But in this day and age, we're so used to the standard use of 24mm and 35mm prime lenses that it's easy to forget the origin of the 28mm focal length.

I remember how 28mm was the standard wide angle in the analog days of photography. The 24mm lenses existed but were extremely expensive and in comparison rare. You would choose a 50mm as the standard focal length or the 28mm for a wide angle.

More importantly, the 24mm field of view is sometimes considered a bit too wide for many occasions. You need to get close to the subject, which makes it prone to perspective distortions. Alternatively, the field of view of a 35mm is too narrow. For prime lens users, the 28mm sits perfectly in the middle.

The Canon RF 28mm f/2.8 STM in Detail

This lens is extremely small, measuring only 69.2 x 24.7 mm, and it weighs only 120 grams. It's truly a pancake lens, the very first one I've used. Although its length is less than 2.5 centimeters, Canon found room for a multifunctional ring and a switch. The switch offers the choice between manual focus, autofocus, and the control function set by the camera's customization menu.

The ring is positioned at the front of the lens and measures only a few millimeters in width. Thanks to the structure of the ring, it's easy to operate. There is almost no need to worry about getting fingers in front of the lens. When looking at it, the front lens is tiny and makes up only a small part of the diameter. If you like to use filters, 55mm is the size you need.

Focus is achieved with an STM motor. It is fast and accurate, but not completely silent. You hear the lens focusing, but the sound is not obtrusive. If there are environmental noises, it’s inaudible unless you put your ear next to it. The minimum focus distance is 23 centimeters. It offers a 0.17x magnification at that distance.

A Look at the Image Quality

As mentioned on the Canon website, the lens has three aspherical lens elements with a Super Spectra Coating. These are responsible for maintaining image quality with a small lens design like this. The image is not flawless, but it relies on in-camera lens correction to obtain the best possible quality.

Image sharpness looks good, especially in the center of the frame. At the extreme edges, it loses sharpness, no matter what aperture you use. This is most noticeable on a full frame sensor.

Vignetting and Distortions

Without lens correction enabled, the RF 28mm f/2.8 STM shows the expected vignetting at f/2.8. This vignetting is almost gone at f/8, but not completely. Even at f/11, it shows some light falloff at the edges. 

The lens also shows strong barrel distortion. Both vignetting and distortions are removed with in-camera lens correction enabled, showing how this lens design depends on this correction.

Chromatic Aberration and Flares

I noticed how little chromatic aberration this lens shows, even without lens corrections. Since this lens performs best with in-camera lens correction enabled, I checked the amount of chromatic aberration in a real-world situation. At f/2.8, it seems to show a hint of purple fringing, which can be easily removed in software like Lightroom Classic.

The RF 28mm f/2.8 STM does show some flaring, but it seems to be reasonably well under control. The 7 diaphragm blades produces an acceptable star with 14 points.

Bokeh

At f/2.8 and 28mm focal length, you can't expect to get an amazing bokeh. But the round diaphragm opening does produce nice bokeh circles. There is not much deformation of these circles, and I didn't notice any onion ring effects.

It is possible to achieve a reasonably small depth of field at f/2.8. This makes it possible to have a nice separation between foreground and background without losing recognizability.

Real-Life Experience

Because of its small size, the RF 28mm f/2.8 STM makes any Canon EOS R camera discreet, except perhaps the Canon EOS R3. While the lens has a 28mm field of view on a full-frame camera, it changes to a 45mm field of view on an APS-C camera. In both situations, it's a great focal length.

I personally experienced one downside, and that's its size. The pancake lens feels too small for my preferred way of holding a camera. Of course, this is personal, and perhaps it needs getting used to in order to appreciate this kind of lens.

I used the lens on both a Canon EOS R5 and a Canon EOS R10 for some street photography and simple landscape and nature photography. This is where I noticed the benefit regarding its size and weight. At 120 grams and only 7 x 2.5 centimeters, there is no reason to leave it at home. It won't take up a lot of space in the camera bag.

Colors and sharpness are better than expected. Keep in mind how the sharpness will decrease at the edge of the frame. As mentioned before, its focal length is a perfect match, not as wide as 24mm but wider than 35mm. When using it on an APS-C camera, it matches almost a 50mm field of view, which is perfect.

Conclusion

I do like this lens a lot. Its image quality is good, even better than what I expected. Although it shows some flaws, the in-camera lens correction is able to correct it.

The lens is easy to take with you. Mounted on a camera, it's discrete, making it an ideal lens for street photography and travel photography. The bokeh looks nice, although you shouldn't expect wonders from it. 

These lenses are, for the most part, made out of plastics, but they show good build quality. The control ring is easy to use, and thanks to the switch, you can use it for more than one purpose.

What I Like

• Small and compact, easy to take with you
• Only 120 grams
• Control ring with switch for more functionality
• Good build quality, even though it's mostly plastic
• Focuses quickly and accurately
• Good image quality, except in the extreme corners
• Large aperture

What Could Be Improved

• The length is not everybody's cup of tea
• It's focus by wire and changes length when reaching minimum focus distance
• $299 feels a bit expensive for such a lens

Do I recommend the Canon RF 28mm f/2.8 STM? If you are into prime lenses, yes, absolutely. It's a great focal length, both on full frame cameras and APS-C cameras, and you won't be disappointed in the image quality. I think it's a great companion for a set of lenses that include the RF 50mm STM and the RF 85mm STM.