LED TV Picture Screen Uniformity Problems and Solutions
by Phil Conner
We review an awful lot of TVs, more than any other TV reviewers (tied with CNET). We've also been testing TVs since year 2000 so we feel fairly certain about our opinions regarding technical difficulties. Screen uniformity issues pop up frequently with LED TVs. Plasma TVs have no such problem due each plasma pixel being individually lit. The only way there could ever possibly be an issue would be for on side or portion of the screen to be receiving more power. LCD TVs with fluorescent backlighting have had screen uniformity issues in the past where one could see where the backlighting was located by a faint white shadow. This issue with LCD Televisions was nor is frequent.
LED TVs have been a bit plagued by the issue. There are almost no LED televisions in the market place that do not have some issue with uniformity, but it has gotten better in some TVs this year. The backlighting is normally placed at the sides of the panel in 95% of LED TVs. These are naturally called edge-lit LED TVs. Screen light imbalances occur when one portion of the screen is brighter than others, thus causing serious issues with color and black levels. This technical deficiency occurs with both matte and clear coat finish LED panels from our experience. The left and right edges of the screen are slightly brighter than the center of the screen, thus creating the problem.
But how much of an issue is it? You hear from sales people how great the new LED TVs are, right? First of all I would like to point out that the problem results from a technological breakthrough in LED backlighting. LEDs are brighter, use less energy, and last longer than do their flourescent counterparts. Next, consider that the screen uniformity issue is only there due to the much brighter LED lighting. So the fix is simple. Every LED TV has a backlight adjustment. We frequently recommend following our calibrated picture settings for your TV, with the only adjustment being the backlight depending upon room light conditions. In darker room lighting turn the backlight down to 60% and poof! the screen light uniformity issue is practically gone. In brighter rooms, fight ambient light by turning up the backlight. You wont notice the screen uniformity issue here either because of the surrounding light. Lastly, LED TVs generally lose contrast levels at angles. Screen uniformity imbalance is also apparent from side viewing angles, so stay more in the center viewing area - preferably at eye level.
Grey Uniformity on an LED TV
The following LED TV models have tested fairly well among the rest in the screen uniformity and side viewing angle areas:Sony KDL55HX850 Sony KDL46HX750 LG 55LM7600 Samsung UN55ES6500 (and UN55ES6580) Samsung UN55ES8000
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