You can almost set your seasonal clock by the release of a new GoPro camera. This year is no different; pandemic notwithstanding, the Hero 9 arrives precisely as the weather starts to cool.
Last year's Hero 8 brought a new cageless design with built-in mounting rings and a more compact front lens. This year takes that form and enlarges it slightly. The Hero 9 is larger in all dimensions, though not noticeably heavier. It also fixes one major flaw in the Hero 8's design: The lens cover is now replaceable (should you scratch it).
GoPro didn't stop there, though. It's now possible to add alternative lenses. At the moment, that means you can attach GoPro's $100 Max Lens mod (sold separately), which brings half of the field of view found in GoPro's 360-degree Max camera. Pair that with a new sensor that captures 5K video, a full-color front screen, and the ability to pull 14-megapixel stills from video, and you have a compelling reason to upgrade if you haven't done so in a few years.
The first standout feature in the Hero 9 is the 23.6-megapixel sensor. That's quite a jump from the predecessor's 12-megapixel sensor. More megapixels means the Hero 9 Black can shoot 5K video and snap 20-megapixel still images.
5K video on its own isn't that useful for most of us, since very few devices or streaming services support anything over 4K, but the extra pixels mean you can crop your video and still end up with 4K footage. With the huge field of view in a GoPro, the ability to crop and zoom in on your subject after the fact is a tremendous advantage.
The disadvantage is that you're limited to 30 frames per second (fps) in 5K, whereas at 4K you can shoot 60 fps. That means for fast-paced action—think Hero 9 strapped to your head while snowboarding a narrow chute—you're likely better off switching to the lower resolution and higher frame rate. For broader shots with less motion, the higher resolution at lower frame rates will be better, opening up cropping possibilities when you edit.
The other downside with shooting at 5K is that most mobiles devices aren't capable of playing it, so there's no previewing in the mobiles app. You'll have to download the footage to your laptop or desktop.
The 20-MP still images are perhaps an even more noticeable step up from previous Hero sensors. RAW images are considerably sharper, and there's less smearing of fine details. The physical limitations of small lenses aren't gone—purple fringing is quite common but easy to remove with software.