ISO 50 normal photo
I'm usually shooting full resolution photos in sunny days.
To minimize the noise I set the ISO to 50. The first photo is OK with ISO 50.
Now when I close the camera app and start it after a while again to shoot with the same settings, the ISO 50 photo gets darker.
When I set ISO 100 the image gets even darker instead of brighter.
ISO 200 doesn't help as well- almost black.
Workaround: reset ISO to Auto and then choose 50 again.