The camera now has a 1/1.3" sensor (up from 1/1.7") and can record gyroscopic data. Also, it has a tougher case and other improvements - but a higher price too.
DJI's Osmo Action 4 launches at $399 - The Verge
Osmo Action 4 4K/120fps Camera Standard Combo – DJI Official Retail UK
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DJI Launches Osmo Action 4 Camera With Larger Sensor And Better Stabilization News 03 Aug 2023
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DJI launches Osmo Action 4 camera with larger sensor and better stabilization - news
Osmo Action 4 4K/120fps Camera Standard Combo – DJI Official Retail UK
DJI Osmo Action 4 4K Camera Adventure Combo (90021090187)