10-16-2016 07:16 PM
This most certainly is not expected from a Hero4 Black. As you know, ISO 380 (I'm assuming you have the ISO limit on) should not give you this much noise in your picture.
Just to put the ISO issue to bed, can you take a few pics with the ISO locked?
My assumption is there is an issue with the sensor and you will need to contact GoPro customer service directly. PKBContactus
Having a few pictures with locked ISO should help demonstrate your issue.
Please do the following:
1) Use only a recommended SD card (I recommend Samsung Pro/Pro+ or Lexar 1000x or 633x) /microSD-Card-Considerations
2) Run a manual update on your camera (even if it is already on the latest firmware) https://gopro.com/update/hero4
3) Format your card in the camera
4) Take pictures with ISO locked at 100, 200, 400 same subject, same lighting
GoPro should be able to help you out.