GoPro HERO 4 BLACK Mode D'emploi page 66

/ Protune
ISO LIMIT
ISO Limit adjusts the camera's sensitivity in low-light environments,
and creates a balance between brightness and resulting image noise.
Image noise refers to the degree of graininess in the image.
Protune for Video ISO Limit
Setting
6400 (default)
1600
400
66
Lighting Condition/Resulting Quality
Brighter video in low light, increased
image noise
Moderately bright video in low light,
moderate image noise
Darker video in low light, reduced
image noise