Blurred Image or some stains appear on my Dome camera, only by night, what should I do ?

Only by night, you notice a degration of image quality of your Dome cameras, whereas during the day, everything is clear

Examples : Blurred image, fog effect, stains...

The problem is often related to the reflections of the IR LEDs inside the camera.

Please check : 

1- The camera is not fixed well : Check the base of the camera and the glass of the cover and check the tightness. Condensation can then appear at night and then disappear during the day when temperatures rise. You can wipe down your camera with a microfiber cloth and use an anti-fog spray.

2- Dust, dirt or micro scratches may appear :  Regularly clean the camera and remove the rainwater stains

3- Damaged or incorrect fixed rubber ring :  The rubber ring around the camera lens must be perfectly clean, undamaged and must fit perfectly against the glass of the cover. Otherwise, reflections may appear.

4- Camera Rotation Limit : Most of Dome camera has a maximum angle of rotation to respect and the IR LEDs must still remain visible otherwise, reflections inside camera may appear.