The resolution of the screen may be a big deal when it comes to picture quality, but almost just as important as the resolution is the way in which the screen is lit. In the past, technologies like plasma screens and LCDs with CCFL lighting were common, but you would have a hard time finding a model that uses either of these technologies today. The most common form of lighting that you will find today is LED backlighting, but there is also a newer technology called OLED lighting.
The vast majority of TVs on the current market have an LCD screen that is illuminated by using some form of LED backlighting. The LCD screen contains all of the pixels that make the screen image, but they need a light source to illuminate the image. Previously, this was done by using fluorescent lamps and these lamps were replaced by the more compact, efficient and dynamic LED lighting.
As a basic description, the LCD screen is made up of millions of pixels and all of these pixels have what are known as sub-pixels. These pixels control the amount of light that passes through and the sub-pixels apply colours as the picture source demands. The LEDs supply the light that brings these images to life. That being said, there are some issues.
The pixels on an LCD screen can filter out or block most of the light from the LEDs when the picture calls for a deep black, but they cannot block 100% of the light. That means that you cannot get true blacks and it leads to a limited contrast ratio on the screen. This can cause issues with depth and clarity on the screen and it can also make it difficult for the screen to accurately reproduce scenes where there are both images of high brightness and deep darkness in the same setting.
Manufacturers of LED TVs have come up with a way to address this issue and that is by using a technique called local dimming. With local dimming, the array of LEDs that are behind the screen are broken up into different zones that the TV controls separately. That means that the lighting behind one part of the screen can be bright, while the LEDs behind another part of the screen go dim.
With TVs that used LED backlighting, you may also want to consider the positioning of the lights. With some models, the screen is direct-lit, meaning that the LEDs sit directly behind the screen. With others, the screen is edge-lit, meaning that the LEDs are positioned at one or more of the sides. For lighting uniformity, direct-lit screens tend to be a little better, but edgelighting allows the manufacturer to produce a thinner TV. In addition to this, a screen with the lights positioned directly behind the screen will lend itself better to local dimming, whereas one that uses edgelighting is going to be less capable using this effect.
OLED is the newest screen technology and it has a lot of advantages over the LCD screens that use LED lighting. With an OLED screen, there is no backlighting; the pixels emit their own light source. With each pixel being able to light up or turn off independently, you get more accurate colour reproduction and better contrast. This means truer blacks and even better shading for an experience that has more depth and definition.
The OLED screens also respond much faster than LEDs. That means less motion blur and the ability to handle dramatic changes in the onscreen image without distorting or leaving artifacts behind. Of course, a low-quality source may still have these problems with an OLED TV, but it is a problem with the source and you would have the issue regardless of the screen type.
In addition to that, these screens are also much thinner than LED screens. Without the need for a backlight, the screen can be ultra slim. When you look at an OLED screen, it is almost paper-thin and it makes for a really nice looking piece of electronics.
The OLED screen technology may allow for deeper blacks and better contrast, but there is one way in which LED backlighting does perform better. A screen that uses OLED lighting is going to be able to achieve a better peak brightness. As you would assume, this can make for brighter colours and images when the source calls for it.
An OLED screen will have several advantages over screens that use LED lighting, but manufacturers have developed a variety of different technologies that can bring them close in many of the areas where they get outperformed by the OLED technology. If you buy a top of the line model that uses LEDs, it is likely to perform just as well when you consider all of the factors that make for a good picture quality. Additionally, OLED TVs tend to be much more expensive.