Engineering is a series of compromises, accepting some bad things to permit other good things. Nothing can be perfect for everything, and close-to-perfect things are really expensive. The Canon RF 16mm f/2.8 is marketed as “compact, versatile, speedy and affordable”, and these outline the compromises in its design. In my brief one-week rental of the lens, I encountered all of these, and my overall impression is that it’s good for what it is. You shouldn’t expect miracles; it’s not the $2400 RF 15-35mm f/2.8. The RF 16mm f/2.8 is only $300. That is very good for a camera system mainly consisting of lenses in the $1000-$2000 or more range.
The lens body of the 16mm f/2.8 itself is the same as the RF 50mm f/1.8, taking advantage of the economies of scale of that so-called standard lens’s mass production. That is part of what makes it cheap. It is small, something only possible because of the 20mm flange distance of the mirrorless RF mount, which allows larger lens elements to be placed closer to the sensor. This is an advantage over DSLRs, which require about twice the flange distance to account for the mirror box. This distance makes ultrawide lenses on DSLRs larger and more expensive, out of reach for a hobbyist.
First, two good things about the Canon RF 16mm f/2.8. The f/2.8 aperture is nice and bright and allows you to have a very short depth of field that results in beautiful bokeh and use lower ISOs for cleaner images.
Another good thing about the lens is its fast and accurate autofocus. Other RF lenses I have used with the STM-type motor have lots of trouble finding focus, particularly at close distances. I didn’t have that problem with the RF 16mm f/2.8 STM.
With the lens body, we arrive at the first major compromise of the design. The lens only has one adjustable ring on it which combines the manual focus and control rings, which acts as a third programmable dial on the camera for changing settings such as white balance, ISO, and exposure compensation, among others. The lens body only has one switch, which changes the behavior of the ring between control and focus. I don’t mind this compromise, because I don’t use the control ring or manual focus often.
The most significant compromise of the lens is in the optical design: nine elements in seven groups according to the specifications. Technically, the image quality is not good. The barrel distortion, an aberration where magnification decreases from the center of the image, is so bad it’s almost like a fisheye lens. Vignetting, where corners of the image are dark because the lens does not illuminate them, is also not great. The ability to turn off in-camera corrections is disabled both for raw images, JPEGs, and in Canon’s official software because of this.
If you go out of your way to open a raw file without any lens or camera corrections using third-party software you will see these problems. In-camera corrected JPEGs look fine, except in the corners, which are stretched to correct for the barrel distortion. At f/2.8, the corners of the image are soft and even show coma on point sources at the edge. This gets a little better at f/11, the diffraction limit for the sensor on the Canon EOS RP. The center of the image, most important to most photographers, is good at f/2.8.
Another compromise is that the lens does not have optical stabilization, but that’s not a big deal. Stabilization would have increased the price a lot, and the large aperture still permits short exposures to avoid blurring due to vibrations. Stabilization is more of a concern for longer focal length lenses where a tiny vibration can result in a lot of blurring in the image.
Canon also markets this lens for astrophotography, but I did not get a chance to take the one I rented out under the stars due to clouds. [Ed note: Shocked. Shocked I am.] My rental lens also did not include the Canon-made lens hood as it is currently in short supply, like many other things due to the current pandemic supply chain crunch.
Like all non-L series lenses, Canon does not include a lens hood with the RF 16mm f/2.8. Hoods are important for ultrawide lenses to effectively control flare, but I didn’t have any problems without one. In general, I don’t use Canon-made hoods. Third-party lens hoods are just as good for a small fraction of the price of the official ones.
I’m going to conclude my review with one more good thing about the Canon RF 16mm f/2.8. It has a higher than average reproduction ratio of .25x, meaning that you can fill the frame with something 144-mm wide at the minimum focus distance of 13 centimeters. 1x magnification is defined as filling the frame with something the size of the sensor, or 36 millimeters wide for a full-frame camera like the RP. While not a real macro lens, having that magnification on an ultrawide lens is novel and is a useful feature for closeups, which is what I like using an ultrawide lens for.
Overall I was happy with the RF 16mm f/2.8, but it’s kind of a specialized lens that most people probably won’t need to have but could buy with little justification because of its low price. At $300, it’s very affordable and has decent image quality, especially with camera-corrected JPEGs. It’s not a lens aimed at professionals and doesn’t try to be.
If you want to purchase one after listening to this review, you can do so from Amazon using our affiliate link which will be in the show notes for this episode.