Autofocus and Stabilization

Autofocus courtesy of the RF 35mm F1.8's STM motor is reasonably speedy, but not quiet, and video shooters will find that some focusing sound is recorded in captured footage. Built-in optical stabilization is very effective for around 3 stops, which makes this lens highly versatile on current EOS R bodies, neither of which offer in-body stabilization.

Key takeaways:

  • Autofocus is moderately fast but not quiet
  • Optical stabilization is good for ~3 stops in normal use
  • Dual Sensing I.S. system allows sharp handheld 1sec exposures
  • Lens extends by ~3/4 inch at minimum focus distance
  • No focus window or distance scale

Autofocus

Canon has opted to use an STM motor rather than an USM motor to take care of autofocus. This is a gear-type motor used in other compact lenses, rather than the screw-type STM alternative used in other macro lenses such as the EF-M 28mm F3.5 Macro IS STM and EF-S 35mm F2.8 Macro IS STM.

The inner barrel extends by around 19mm, or three-quarters of an inch, when set to its closest focusing distance of 17cm.

The lens doesn’t have internal focus, which is desirable for a macro lens, but the fact that this isn’t a true macro lens makes its absence understandable (something that also applies to the lack of any focus limit switch). The inner barrel extends by around half an inch at the closest focusing distance of 17cm, which means there’s no risk of hitting the subject you may be shooting, and this extension also means it’s highly unlikely to present any lighting issues as it moves. 35mm is also far from a classic focal length for macro work, although the option to apply a 1.6x crop in camera boost effective focal length to 56mm is useful, even if this does come at the expense of final resolution.

All but the rear two elements move during autofocusing, and this means that for large focus changes, the lens just isn't as fast as others that couple a small, lightweight focusing element with powerful linear motors. That said, most photographers will find it speedy enough, even when lighting conditions aren’t great. Paired with the EOS R it delivers nice smooth focus transitions during video recording, but again focus isn't silent, and you may pick up operational sounds on internal audio in quiet conditions.

You won't find a distance scale or focus window on the RF 35mm F1.8, which might alarm some manual focus fans.

There’s no focus distance window or scale of any sort on the lens itself, although an equivalent display pops up on the camera’s LCD and viewfinder when manual focus is selected. Incidentally, full time manual focus is possible if you enable this on the camera, and the EOS R also offers a useful focus guide that uses triangles to show when the subject you’re shooting is in focus, in addition to a peaking option.

The lens works on a focus-by-wire system, and there’s barely any resistance from the focusing ring as it's turned, although I personally found that the lens can be focused manually without any issue. A Custom Option allows you to switch to linear focus response, whereby the focus is adjusted in accordance with the degree of ring rotation rather than the speed of the rotation which provides a far more manual-like focusing experience - something that is especially useful in video mode. Whichever way you choose, the system works perfectly well with the focus peaking options on the EOS R, and the option to magnify into the scene as you make adjustments is useful, although some might wish that it was possible for both to operate at the same time.

Image Stabilization

Canon doesn’t currently offer sensor-based stabilization in its EOS R-series bodies, but the RF 35mm F1.8 is optically stabilized, using a Hybrid system. Hybrid I.S. makes use of an accelerometer to correct shift movement – a particular concern with macro shooting – in addition to two gyro sensors that handle angular movements.

Aside from the control and focus rings, the only controls on the RF 35mm F1.8 are a simple AF/MF toggle and an I.S. switch.

Image Stabilization performance is further boosted through a Dual Sensing I.S. system, something Canon has previously used in its PowerShot G7 X Mark II and EOS M50. While correction still happens inside the lens, the data from the gyro sensors inside the lens is augmented by information from the main imaging sensor, which Canon states makes it easier to correct for low-frequency shake. When panning, the system can correct for vertical shake when panning horizontally, and vice versa, while lens-based stabilization works with the digital 5-axis Electronic IS option to deliver Combination I.S. when shooting videos.

As a general rule, image stabilization is less effective as the subject distance decreases, but with this system on board Canon reckons the system can still provide a benefit of 3 stops when shooting at the maximum 0.5x magnification, which works out at about 1/5sec. For more general use, the system has a CIPA rating of 5 stops, which should make it possible to capture images with acceptable sharpness as shutter speeds as low as around 1sec.
Much of your success here depends on the specific circumstances.

With care, it is possible to hand-hold the RF 35mm F1.8 at shutter speeds as low as 1/3sec without a loss of sharpness, even shooting in the closeup range.

ISO 100 | 1/3 sec | F4
Photo by Carey Rose

The system is certainly effective when shooting close-up, although, perhaps unsurprisingly, I enjoyed a higher hit rate at slower shutter speeds in warmer indoor environments than outside. Indoors, I found it possible to achieve acceptably sharp images at 1/6sec with the lens focused at its closest focusing distance, although not quite as consistently as at 1/8sec and 1/10sec. Outdoors, it only seemed possible to capture the odd image sharply at around 1/15sec, with 1/20sec being a better bet for consistency.

At its minimum focus distance, the RF 35mm F1.8 is a good performer at medium apertures, and while 35mm isn't necessarily a classic macro focal length, it's easy to capture high-quality closeups. By F5.6, images in the macro range are very sharp, crisp, and free from the slight haziness and fringing which can be visible wide open.

ISO 100 | 1/2 sec (tripod) | F5.6

With the lens focused to infinity, I was surprised at how well the stabilization managed to do at the promised 1-second goal. While it was difficult to achieve consistency when shooting at 0.5sec and slower, a very good proportion of images captured across 0.5sec, 0.8sec and even 1sec shutter speeds were acceptably sharp. This also opens up opportunities to capture sharp images with blurred elements, which will no doubt please street and documentary photographers who would prefer not to use some kind of physical support.