A firmware update was recently released for the NVR6XX-4KS2 series devices.
Information, instructions, and download links can be found Here
Troubleshoot/NVR/Troubleshoot Blurry Camera
From Dahua Wiki
Camera Feed is Blurry or Distorted
There are following possibilities:
- It maybe that the camera is out of focus. The real*time video becomes black and white.
- If DVR and monitor resistance is not compatible then use a different monitor/DVR.
- If Video transmission is too long or degrading is too huge then shorten the distance.
- If DVR color or brightness setup is not correct then readjust setup or default.
- If Resolution or stream is on low then adjust resolution or stream.
- If Image sensor is bad then replace image sensor.
- Direct Sunlight can cause image sensor to go bad. So place image sensor out of direct sunlight.
- Try to avoid mounting camera on a metal surface. Electrical bleeding from a power source can cause image distortion.
- Indoor Camera being used as an outdoor camera which might not have an IR cut filter.