Industry info - The Contrast of LED and OLED
Time:2023-03-14
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How do they differ?
In a nutshell, LED LCD screens use a backlight to illuminate their pixels, while OLED‘s pixels produce their own light. You might hear OLED‘s pixels called “self-emissive”, while LCD tech is “transmissive”. The light of an OLED display can be controlled on a pixel-by-pixel basis. This sort of dexterity isn’t possible with an LED LCD – but there are drawbacks to this approach, which we‘ll come to later. In cheaper TVs and LCD-screen phones, LED LCD displays tend to use “edge lighting”, where LEDs sit to the side of the display, not behind it. The light from these LEDs is fired through a matrix that feeds it through the red, green and blue pixels and into our eyes.
Brightness
LED LCD screens can go brighter than OLED. That‘s a big deal in the TV world, but even more so for smartphones, which are often used outdoors and in bright sunlight. OLED TV playing a movie, displaying a man pointing a gun towards a man held by Batman and fire behind him. Brightness is generally measured as "nits" – roughly the light of a candle per square metre. Brightness is important when viewing content in ambient light or sunlight, but also for high dynamic range video. This applies more to TVs, but phones boast credible video performance, and so it matters in that market too. The higher the level of brightness, the greater the visual impact.
LED LCD wins
Contrast
Take an LCD screen into a darkened room and you may notice that parts of a purely black image aren‘t black, because you can still see the backlighting (or edge lighting) showing through. Being able to see unwanted backlighting affects a display‘s contrast, which is the difference between its brightest highlights and its darkest shadows. You‘ll often see a contrast ratio quoted in a product‘s specification, particularly when it comes to TVs and monitors. This tells you how much brighter a display‘s whites are compared to its blacks. A decent LCD screen might have a contrast ratio of 1,000:1, which means the whites are a thousand times brighter than the blacks. Contrast on an OLED display is far higher. When an OLED screen goes black, its pixels produce no light whatsoever. That means an infinite contrast ratio, although how great it looks will depend on how bright the screen can go. In general, OLED screens are best suited for use in darker rooms, and this is certainly the case where TVs are concerned.
OLED wins
Viewing Angles
OLED panels enjoy excellent viewing angles, primarily because the panel is so thin, and the pixels are so close to the surface. You can walk around an OLED TV or spread out in different spots in your living room, and you won‘t lose out on contrast. For phones, viewing angles are extra important because you don‘t tend to hold your hand perfectly parallel to your face. Viewing angles are generally worse in LCDs, but this varies hugely depending on the display technology used. And there are lots of different kinds of LCD panel. Perhaps the most basic is twisted nematic (TN). This is the type used in budget computer monitors, cheaper laptops, and very low-cost phones, and it offers poor angled viewing. If you‘ve ever noticed that your computer screen looks all shadowy from a certain angle, it‘s more than likely it uses a twisted nematic panel. Thankfully, a lot of LCD devices use IPS panels these days. This stands for "in-plane switching" and it generally provides better colour performance and dramatically improved viewing angles. IPS is used in most smartphones and tablets, plenty of computer monitors and lots of TVs. It‘s important to note that IPS and LED LCD aren’t mutually exclusive; it‘s just another bit of jargon to tack on. Beware of the marketing blurb and head straight to the spec sheet.
OLED wins
Colour
The latest LCD screens can produce fantastic natural-looking colours. However, as is the case with viewing angles, it depends on the specific technology used. IPS and VA (vertical alignment) screens offer great colour accuracy when properly calibrated, whilst TN screens can often look weak or washed-out. OLED‘s colours have fewer issues with pop and vibrancy, but early OLED TVs and phones had problems reining in colours and keeping them realistic. These days, the situation is better, Panasonic‘s flagship OLEDs are used in the grading of Hollywood films. Where OLED struggles is in colour volume. That is, bright scenes may challenge an OLED panel‘s ability to maintain levels of colour saturation. It‘s a weakness that LCD-favouring manufacturers enjoy pointing out.
LED LCD wins
