Canon RF 16mm F2.8 STM Review
The Canon RF 16mm F2.8 STM is an affordable ultra-wide-angle prime lens for Canon EOS R full-frame mirrorless cameras that won't break the bank.
This is an extremely compact and lightweight lens, yet it still offers a bright maximum aperture of F2.8 for better low-light performance and bokeh effects.
It features 9 elements in 7 groups, including one aspherical element helps control distortion, and it has a Super Spectra Coating to help reduce flare and ghosting, plus a 7 blade diaphragm which creates an attractive blur to the out-of-focus areas of the image.
An internal focusing mechanism means the lens barrel doesn't move, and it offers an impressive minimum focusing distance of 13cm / 5.1" and a maximum magnification ratio of 0.26x, whilst using cost effective 43mm filters.
Aimed predominantly at vloggers, astro and landscape photographers, the Canon RF 16mm F2.8 STM lens is available now priced at £319 / $299 in the UK and the US, respectively.
Ease of Use
Weighing in at 165g / 5.8 ounces and measuring 4cm in length, the RF 16mm F2.8 STM is a super-light, tiny ultra-wide-angle prime lens.
It's barely noticeable when used with a mid-sized camera body like the Canon EOS R6 body that we tested it with, as shown in the product photos.
The lens barrel automatically extends by an additional 5mm when the camera body is turned on and then retracts back into the housing when the camera is switched off.
Build quality is good for such an affordable lens. Despite its mostly plastic construction, the RF 16mm F2.8 STM feels solid in your hand, and it commendably has a metal mount.
Note that this lens does not have a weather-resistant design to help protect it against dust and moisture.
There's also no optical image stabilizer built-in to this lens, though arguably you don't really need this feature on such a small and light wide-angle optic.
If you're not using the focusing ring for manual focusing, you can change its operation to be the Lens Control Ring instead via the dedicated Focus/Control switch on the side of the lens barrel.
In this Control setting, the ring can be used to control certain key camera settings (TV, AV, ISO and exposure settings) instead of the focusing. Although not a new idea in the wider photography world, this is one of the first times that Canon have incorporated this idea into their interchangeable lenses.
The Canon RF 16mm F2.8 STM lens has a rather narrow fly-by-wire focus ring with a ridged grip band.
There are no hard stops at either ends of the range, making it more difficult to set focus at infinity.
Note that this lens usefully offers full-time manual focusing even when AF is selected.
In use the manual focusing system emits an audible "whining" noise that makes it less suitable for video than stills.
Polariser users should be pleased that the sensible 43mm filter thread doesn't rotate on focus.
When it comes to auto-focusing, the RF 16mm F2.8 STM is a snappy performer thanks to the STM motor, taking around 0.10 seconds to lock onto the subject when mounted on the Canon EOS R6 camera that we tested it with.
We didn't experience very much "hunting" at all, either in good or bad light, with the lens accurately focusing virtually all of the time, thanks to the superb low-light capabilities of the EOS R cameras.
The STM motor is also pretty quiet in AF mode, emitting a much quieter "whirr" than when manually focusing, which makes this lens well-suited to auto-focusing during video recording.
There is a petal shaped lens hood (EW-65C) and a soft case (LP1014) available for this lens, but disappointingly both are optional extras that aren't included in the box.
The Canon RF 16mm F2.8 STM's focal length of 16mm provides an angle of view of 108°10.
Chromatic aberrations, typically seen as blue or purple fringes along contrasty edges, were not especially apparent in our test shots, only appearing in very high contrast areas.
When shooting JPEGs, with the lens set to its maximum aperture of f/2.8, there is some obvious light fall-off in the corners, requiring you to stop down by at least 2 f-stops to prevent it.
There's a huge amount of vignetting evident in the RAW files, though, with almost pure black in the extreme corners - thankfully the Canon EOS R6 camera automatically and successfully applies corrections to the JPEG files, resulting in an acceptable out-of-camera image.
There's a frankly incredible amount of barrel distortion evident in the RAW files - thankfully the Canon EOS R6 camera automatically and successfully applies corrections to the JPEG files, resulting in an acceptable out-of-camera image.
Note that you cannot actually turn off distortion correction in an EOS R camera body when this lens is used - the menu option is actually greyed out and unavailable - which gives you a good idea of just how much correction the camera is applying!
You will need to use Canon's Digital Photo Professional 4 software to post-process the Raw files, at least until Adobe releases an RF 16mm lens profile for Camera Raw / Lightroom.
Sunstars and Flare
The Canon RF 16mm F2.8 STM is capable of creating some very nice sunstars when stopped-down to f/22, as shown below, and flare is also well controlled even when shooting directly into the sun.
The Canon RF 16mm F2.8 STM offers a very useful minimum focusing distance of just 13cm / 5.1", with a maximum magnification of 0.26x.
Bokeh is a word used for the out-of-focus areas of a photograph, and is usually described in qualitative terms, such as smooth / creamy / harsh etc.
In the RF 16mm F2.8 STM lens, Canon have employed an iris diaphragm with 7 rounded blades, which has resulted in quite nice bokeh in our view for such a wide-angle lens.
We do realise, however, that bokeh evaluation is subjective, so we've included lots of examples below for your perusal.
In order to show you how sharp the Canon RF 16mm F2.8 STM lens is, we are providing 100% crops on the following page.