Example of the proceeding in Nvidia Shadowplay:
1.Start DayZ
2.Start recording
3.Stop recording
4.Capturing is darker than the original picture

When changing the render resolution while recording, the problem is fixed until you stop the capture.

Another way to fix the problem temporary is pressing ALT and TAB at the same time and returning after that back to DayZ. It's just working while recording. When stopping the capture, the problem is still existing.