Mura effect is a term colloquially known as "clouding." Nearly any liquid crystal flat panel display runs the risk of displaying this screen defect. Although common, it can be nonetheless annoying, especially for a new LCD owner expecting perfection. Mitigating mura is something that be accomplished without the assistance of a service tech and requires a little familiarity with the set's picture setting menus.
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Enter the set's menu system. Press the "Menu" or "Setup" button the on the remote control. Access the "Picture" or "Screen" settings in the submenus to access the settings. Consult the manual for model-specific button sequencing for this.
Reduce the backlight to the lowest tolerable setting. If the minimum setting does not appreciably affect picture quality, leave it there.
Ensure the operating temperature is not excessive. Remove the set from any cabinetry or environment that prohibits or limits the ability of the set to cool normally.
Set the screen to display constantly-changing images. For monitors, this means using a screensaver. For LCD televisions, try to ensure that the onscreen material is not static or constant and unchanging.