This is just a quick note as I have seen some posts, by those who should really know better, inaccurately describing the size of the sensor in the new DJI Action 4.
Sensors sizes are typically described in inches and fractions of inches (like TVs are still sadly – probably so that our United States of Americaland friends don’t get too confused). But the nomenclature of, for example 1/2.3 does NOT mean 1″ PLUS 2/3″. A sensor of this size is 7.93mm diagonally as compared to a 1″ sensor which is 16mm diagonally – far bigger. The formula used is actually 1 divided by 2.3. The size of the image available depends on the aspect ratio being used to further muddy the issue.
This is a dramatic difference as you can see and means the larger sensor can grab more light, the thing that defines how good a photo is (and what it is like in lower light situations).
If you need an indepth discussion on this, a very good description is at https://commonlands.com/blogs/technical/cmos-sensor-size.