As a result, not every TV has the same level of capability, even if it supports the same HDR formats.Īnd it all comes down to what type of backlighting is used. Not every form of backlight offers the same level of control. There are different formats with varying degrees of granularity, but the end result is that modern media takes this additional brightness control into account, just as it would color and multi-channel sound.īut there's a catch. While that metadata may fall under different format names, like HDR10 or Dolby Vision, the essentials are the same - describing how those dimmable backlights should behave to produce a richer image. This data describes the brightness and backlighting scheme for a given scene or frame of content. With local dimming zones allowing variable brightness to different sections of the display, new media includes additional metadata, beyond simple video and sound. (Check out our articles What is HDR TV, and why does it matter? and What Is Dolby Vision? to learn more.) It's one of the best features on today's TVs, and one we recommend paying attention to when shopping for a TV. You may not know much about the innovation of local dimming, but you've probably heard of the feature it enables: High dynamic range or HDR. Instead of illuminating the entire screen, the LED backlights of a TV can be addressed individually, meaning that they can be turned on or off, dimmed or brightened as needed to provide brighter or darker portions of the TV picture. Today's TVs use a number of backlighting methods, which we'll discuss below, but the biggest change has been the introduction of discrete backlighting zones. Modern backlighting: Local dimming and HDR Since then, LED backlighting has been refined in a number of ways, and there are several options on the market in today's TVs. But with the last CCFL TVs going off the market a decade ago, it's just as likely that TV makers have kept the LED nomenclature around to blur the distinction between LCD TVs and OLED panels, which use a very different (and largely superior) display technology. With this change, TV manufacturers started calling LCD TVs with LED backlight "LED TVs" to differentiate them from the older CCFL-lit models. Instead, they were replaced by one of the biggest innovations in modern TV technology: LED backlighting. But because these lamps generate heat that can damage a display and aren't terrible energy-efficient, they've pretty much disappeared from today's TVs. Plasma screen TVs used the same sort of phosphorescence that CRTs used, meaning that they were also capable of emitting their own light.īut with the advent of LCD-based flat screen TVs, the need arose for illumination, and originally that meant cold cathode fluorescent lamps (CCFL), a technology that's similar to fluorescent and neon lighting. Cathode ray tube (CRT) technology doesn't need one, because it is a light source unto itself. A brief history of TV backlightįor the first several decades of consumer TVs, there was no need for a backlight. And a lot of the improvements we've seen in modern TVs can be traced to the humble backlight. But that backlight has undergone a lot of changes over time - several just within recent years. You'll have an LCD panel to provide much of the image content, and a backlight behind it to provide the light that makes that LCD panel visible and the colors vivid. The details will vary from one manufacturer or mode to the next, but the fundamentals that that technology is based on remain the same.
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