Black Uniformity of TVs

Clouding and Flashlighting

Additional information

LED vs OLED black uniformity

LED backlit LCD TVs are prone to this issue, but it isn't a problem on OLED TVs, because the pixels are self-emitting, and therefore don't need to worry about improper implementation of a backlight.

The cause of flashlighting and clouding

Flashlighting and clouding can occur for a few reasons:

• Poorly designed backlight placement. The type of the backlight and the position of it directly affect the uniformity of the screen. The worst uniformity can be found in edge-lit LED TVs, because the LEDs are only on the edge of the screen. Full-array LED TVs have good uniformity because their LEDs are spread out across the whole screen. This is less true today, though. Some edge-lit TVs have great uniformity. You can learn more about different backlights here.
• Non-uniform frame pressure. Both the LCD screen and the diffuser layers are somewhat flexible. A slight difference in pressure on the frame of the television can change the uniformity of the picture. On some televisions, this can be fixed (see below).
• Uneven intensity of the lighting. Sometimes, the intensity between two lighting components can vary in a set (for example, one LED could be slightly brighter than an LED next to it). This is less likely to happen with a brand new TV but can start appearing over time if some components age and degrade faster than others.

How to get the best results

Flashlighting can sometimes be fixed on some televisions. If your flashlighting issue is caused by an issue with the frame’s pressure, you can adjust it by slightly loosening or tightening the screws behind the edge of the screen. Some televisions do not expose the screws, however, so you won’t have that option with those. You should also keep in mind that a small change in the tightness of a screw can have a big impact on the uniformity of the screen, so be careful if ever you do try this step.

For clouding, there's a pretty simple fix that - while not guaranteed - can have good results. Power on the TV and display a black image. This will allow you to see the lighter spots on the screen. Next, take a soft cloth and massage those brighter spots to improve the uniformity. You should only apply very gentle pressure, just barely touching the screen. You can also try a few different stroking patterns. If you are patient enough, this works surprisingly often, especially on edge-lit TVs.

Alternatively, you might consider returning or exchanging your television. Some models are more prone than others to having issues. Even within the same model, some units can have more of this issue, because of slight variance in the manufacturing or the shipping process. It can be worth trying to exchange it for the same model before going with an entirely different one. Extreme cases of clouding are also covered under a TV's warranty.

Related settings

• Reducing 'Backlight' can help mask the problem by making the whole screen darker.
• The local dimming feature, if the TV is equipped with it, can also help. We talk about local dimming in more detail here.

Other notes

• All LED TVs have black uniformity problems.
• The bigger the LED TV, the more likely it is to have uniformity issues.
• Backlight uniformity issues don't increase over time unless a large amount of stress is put upon the panel (like in the case of a big temperature swing, or if the TV is moved).
• Sometimes, just letting the TV settle for a few days after unpacking it can solve the issue. This is especially true if the TV is laid on the side during shipping/moving.

Conclusion

A TV’s black uniformity refers to how evenly a TV can display black all across the screen. It’s important when watching dark scenes in a dark room, and while most people shouldn’t notice black uniformity issues like flashlighting and clouding, they can become more apparent when the issues are especially bad. You won’t need to worry about these problems in rooms with lights on, though. For each TV, we take a photo of a black frame in order to capture the black uniformity, and then we calculate the color values of the pixels in order to find the standard deviation of the uniformity.

You may be able to remove flashlighting (to some degree) by tightening the screws of the TV’s frame. This can have pretty dramatic effects on the picture, though, so you should be very careful when attempting this. For clouding, gently massaging problem areas with a soft cloth often does a good job of fixing bad uniformity.