Recently, I took a deep dive into the world of high dynamic range (HDR), because it’s a curious new trend in TV technology—as in, equal parts mesmerizing and confusing. There’s a learning curve to understand what HDR offers, especially since the difference doesn’t always pop in fluorescent-lit showrooms. At the same time, HDR-10 sets are starting to become affordable, and what’s sometimes hard to appreciate at a big-box retailer can look quite stunning in your own home.
In many ways, the same can be said about the other major TV standard that we’re seeing more lately: OLED, which stands for organic light emitting diode. It’s being called the future of TV tech, promising deeper blacks, less motion blur, and sexier colors.
Conveniently, OLED screens are also coming down in price. “Affordable” isn’t the right word, but we’re getting there, with the $9,000 55-inch sets of 2013 being succeeded by models as cheap as $2,300 (along with larger screen options for more cash). Some have 3D, others have curved panels, and all of this year’s models have support for HDR modes and 4K resolutions.
So today, we’re continuing to break down the modern screen landscape by breaking down OLED: how does it work and do the technology’s advertised claims hold up? Along with some answers, we also have details about how manufacturers and content producers fit into the current OLED picture.
The blacker the pixel…
You may see the acronym OLED and think you’re not getting anything much different from LED panels already on the market. What is “organic” LED? Is this like shopping for eggs? Should we make a “free range LED” joke?
The short answer: the word “organic” gets to the heart of the OLED difference. It explains how its image-generation differs from the competition.
Consider LED screens, which are themselves something of a misnomer. When you hear about an LED screen, it’s actually an LCD (liquid crystal display) screen but with improved back-lighting technology called LED. In modern LCD screens, liquid crystals are activated by electricity to rotate and allow light to come through each tiny square of the image (or pixel). Light shines through red, blue, and green filters, and these mixes combine for every color in the spectrum from dark to white. If all panels are rotated in such a way, they let no light through for any of the three colors, resulting in “black.”
While this crystal-rotation trick has tons of benefits (cheap price, thin, light materials), LCD screens have their drawbacks, the obvious one being black level. Even if an LCD screen’s crystals are rotated in such a way as to block all color information (and create a “black” pixel), they’re still backlit by a panel. This will always result in a “light bleed” effect that projectors and antiquated CRT screens don’t have to contend with.
An LED version of an LCD screen mostly works the same way, but it uses a superior type of bright back panel. We could get into the weeds about back panels (LED vs. CCFL), but the major difference is that LED panels can drive images that are simultaneously brighter and darker to deliver a greater contrast ratio. Newer LED TVs have what’s known as a “full array” of smaller LED panels, which can be individually dimmed by the TV itself. If a portion of the current scene in a film, show, or game is dark, that portion’s backlight can be dimmed to reduce the amount of light bleed coming through. This will dramatically improve the visible contrast ratio (meaning, how well black sits next to white in an image), but it’s still not a pure black value. Light remains, however dim, behind the liquid crystals.
This fact, among others, has made TV snobs hold tightly to their older plasma TVs. Plasma pixels can run darker, because they are not backlit. However, each of the three individual cells that makes up a pixel on a plasma screen has to be charged slightly in order to make the screen quickly responsive to incoming changes, even when the TV is not trying to represent light or color in that pixel. This means a tiny bit of energy is being transmitted through a plasma set’s blackest-valued pixels, but that value is still usually less than all but the finest LED screens. Plasma sets are no longer being produced by major manufacturers, by the way, since they don’t support resolutions higher than 1080p and have remained costly, heavy, and power-hungry to produce.
Comparatively, OLED’s clearest improvement comes from its utter lack of backlight. Instead, individual OLED pixels are made from an organic material that emits light from within whenever it’s fed electric current. If a pixel receives no current, it emits no light in the red, blue, or green color spaces. This creates the purest black, Nigel Tufnel black.
Once you can deliver pixels with absolute-zero values for color and brightness, you enter a new realm of contrast-ratio territory. Even the littlest hint of light in the blackest part of an image changes the perceptible contrast ratio.
How much? Well, if a screen merits the Ultra HD Premium certification sticker, its pixels must achieve a minimum brightness threshold. That number of “nits” varies based on the lowest black value achievable. If your maximum black level is somewhere between 0.0005 and 0.5 nits, your set will need to reach a brightness maximum of at least 1,000 nits. Get the maximum black level darker than that, and the required brightness maximum is only 540 nits.
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