Canon RF 14-35mm F4 L Firmware Adds Focus Breathing Fix

Several Canon RF lenses have been refreshed with new firmware, but the latest feature is for video only. The Canon RF 14-35mm f4 L, along with several other RF lenses, have received new firmware updates that allow focus breathing to be corrected in camera. But the update isn’t made for frustrated photographers trying to create a focus-stacked image or consistent series, it’s for video. That’s because the new feature works similarly to digital video stabilization and simply crops the footage to keep the focal length consistent as the focus changes.

Focus breathing is the term used to describe the phenomenon where the apparent focal length changes as the lens focuses. If you focus a lens from near to far and it also looks like the lens is zooming in or out a little, that’s focus breathing. Picture a lens that doesn’t use internal focusing: as the lens focuses, the front is actually getting closer or further from the subject, so it makes sense that the composition would change just slightly. Focus breathing still happens with internal focus lenses, you just can’t see that the lens is getting closer or further away because it’s the internal glass pieces that are moving.

Focus breathing is typically considered an issue for video; there are certainly photographers who go about their entire career not worrying about such an issue. But, there are a number of cases when focus breathing can cause issues with stills. When focus stacking, for example, focus breathing can cause issues aligning those photos in post. When shooting a series of photos with the subject coming towards you, focus breathing can also be bothersome. Focus breathing could also make a wide-angle lens appear to be less wide, or a telephoto to have less reach. And, in scenarios where it’s impossible to move your feet to adjust for the differences in composition, focus breathing can be problematic.

Canon’s new focus breathing correction tool fixes this phenomenon in the camera by cropping video so that the apparent focal lengths still match no matter what’s in focus. The setting is found in the “Lens aberration correction” menu on compatible camera bodies, which currently includes just the R6 II, R8, and R50. Lenses compatible with the feature include: 

・RF24mm f1.8 IS STM

・RF15-30mm f4.5-6.3 IS STM

・RF135mm f1.8 L IS USM

・RF15-35mm f2.8 L IS USM

・RF24-70mm f2.8 L IS USM

・RF70-200mm f2.8 L IS USM

・RF14-35mm f4 L IS USM

・RF70-200mm f4 L IS USM

・RF24-50mm f4.5-6.3 IS STM

・RF-S55-210mm f5-7.1 IS STM

Many lenses require a firmware update to activate the feature, including the RF 14-35mm f4 L.

Canon says the focus breathing correction is only used in video because, in most cases, in-camera cropping wouldn’t be beneficial to stills. “Focus breathing is used specifically for video shooting only,” Andrew MacCallum, Senior Manager at Canon USA told The Phoblographer. “This correction compensates for angle of view changes when adjusting focus while recording video. Since Focus Breathing correction is an electronic correction, it would not be beneficial to stills capture.”

Stills photographers are going to shy away from anything that crops the image in camera. I wouldn’t turn a feature like this on if it were available for stills. So I don’t think the fact that the latest firmware update focuses on video should bother photographers.

But, the bigger question is, should Canon’s high-end L series still be suffering from focus breathing? Focus breathing used to happen on almost every lens except for pricey cinema lenses. Modern lenses are getting better at preventing focus breathing from happening, but some lenses are better than others. Photographers often in scenarios where focus breathing comes into play should consider that when choosing a new lens.

I’ve updated our Canon RF 15-35mm f4 review to include the latest firmware update:

At the widest focal lengths, the lens does have some slight focus breathing. It’s minor enough that most photographers won’t notice unless doing something like focus stacking or shooting in a restrictive setting.  But, the focus breathing can be distracting when shooting video. A new firmware update for this lens, however, allows the focus breathing to be corrected in-camera when recording video with compatible bodies. (As of February 2023, those bodies are the R6 II, R8, and R50.) Focus breathing correction is an electronic fix, which means the video is cropped to prevent adjusting the focus from affecting the apparent focal length. Since the focus breathing is most noticeable at 14mm, turning the focus breathing correction on for video can make the lens appear to be a little less wide.

Still, focus breathing shouldn’t really be happening with Canon L lenses considering their prices. It happens with primes like the Canon RF 50mm f1.2 L and a few others. We’d ideally like it to not happen while having Canon retain their lovely character to their otherwise great lenses.