No, it's not just a simple distortion correction filter. A Google research team has been working on eliminating the face-stretching distortion you get from wide angle lenses, without the ugly bending of perspective lines you get by applying regular distortion filters. At SIGGRAPH 2019, the team has presented an algorithm that does just that.
Super wide angle lenses, like the ones that are starting to appear for things like "wide selfie" modes on smartphones, suck in an impressively wide view from such a small lens, but the tradeoff is that things get stretched out toward the edges. This isn't a dealbreaker for most background scenery, but it makes faces look plain weird. It's one of those things you've probably simply got used to and forgotten about.
Applying a simple perspective distortion correction filter can bring back a much more realistic shape to the faces at the edges of the shot, but to do so, it needs to bend the perspective lines of the entire photo. So the faces look better, but any straight lines in architecture or horizons in the background end up weirdly curved.
The team's solution here is to use a content-aware algorithm to work out which bits of the photo are faces or "subject" items, and which are not. The algorithm then creates a perspective correction map for the entire photo, but applies it only to the subject areas, keeping the background lines straight while perspective-shifting the faces.
The results look great, and the team says the system works fast enough to be "interactive." We're not sure if this means it's quick enough to use during video calling given a standard phone handset, or whether it'll correct the preview window as you're preparing to shoot a wide-angle photo. There's no news here about whether the Pixel team will roll this tech into its famously clever camera software in a future update. But if it does, now you know how it works.
The technology is demonstrated in the video below.
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