Assuming you have the latest firmware, there are two different 15 FPS modes on the Z8. Make sure you haven't chosen the C15 mode, as that is JPEG only.
I made the exact same mistake about a month ago taking photos of my grandson playing volleyball. Ended up with 1200+ jpegs when i was expecting NEF. I don’t typically shoot sports and typically less than 12/sec shooting birds. Another “Pilot Error” for this weekend warrior. IMHO, also begs the question if this scenario might be prevented by a firmware tweak? Perhaps a warning such as, “Choosing this setting will change IQ to JPG. Use H/15 to maintain NEF”.
JShulak wrote:
...begs the question if this scenario might be prevented by a firmware tweak? Perhaps a warning such as, “Choosing this setting will change IQ to JPG. Use H/15 to maintain NEF”.
Indeed. The way this currently works is very bad interface design which could certainly be simplified.