Megapixel count is used to measure still image resolution.
For video resolution, horizontal row count is used. For the AS100, the horizontal row count for highest resolution video is 1080. By standards, high definition video can be 720 or 1080 rows... at 16:9 aspect ratio, the AS100 can record a "video window" of 1920 x 1080... or 2,073,600 or about 2 megapixels... and can capture 18.9 megapixel stills.
On the X1000, 4k video also referred to as "ultra high definition" video has a "video window" of 3840 x 2160 and can capture 12.8 megapixel stills.
The video resolution did not go down, it (horizontal line count) increased. Only the still image resolution decreased.
So I've been considering an actioncam, but I've been confused by the specs for the various models on Sony's web site.
The HDR-AS100, currently available for $250, has a sensor size of 7.77mm and gross resolution of approximately 18.9 megapixels
The FDR-X1000, soon to be available for $500, has a sensor size of 7.81mm and gross resolution of approximately 12.8 megapixels. It is also touted as "4K", but it's unclear to a consumer like me what 4K means if resolution is going *down* instead of *up*.
Can anyone explain this? Will the new model be worth the higher price? What's really better about the new model other than the extra 0.04mm of sensor size?