OLED VS LED
SCREEN TECH SHOOT-OUT
What’s the best screen technology? Well, we can safely ignore such things as plasma now — nobody makes them any more. That leaves two basic TV technologies: OLED and LCD.
I am a great fan of OLED, and that’s what I own. But you may have dierent priorities to me.
You see, OLED’s main virtue is that it does blacks better than LCD. Each Organic Light Emitting Diode cell generates its own light, like in a plasma TV. But unlike plasma, the output can be ramped smoothly down to zero and back up again. So you can have maximum brightness in one pixel, and absolute black in the immediately adjacent pixel. In theory. There will always be some diusion of light in the glass of the screen, but it’s close enough.
And that makes OLED ideal for fine viewing of high quality material -- especially UltraHD Blu-ray, and especially in a darkened room, as though you’re at the cinema.
If you’re watching under normal room lights, the screen is lovely and bright and colourful, but no more so than an LCD TV. Indeed, since LCD TVs are lower in cost than the otherwise equivalent OLED models, you may want to trade o this aspect of performance for a larger screen size.
I don’t think some of the TV manufacturers like me referring to their LCD TVs as LCD TVs. They prefer terms like ‘LED TV’. But they are LCD TVs. They use an LCD panel over a backlight. That doesn’t means that all LCD panels are the same, nor that all backlights are the same. But when a special name is used for an LCD TV, it is almost always about the backlight.
A ‘LED TV’ is an LCD TV which uses LEDs for the backlight, rather than older (and cheaper) Cold Cathode Fluorescent Lamps (CCFL). CCFLs were long strips, usually arranged horizontally. If they were behind the picture rather than at the edges, they were in some models engineered to flash on and o in ways to enhance the picture. But that kind of thing has been overtaken by LEDs.
The first LED TVs used a grid of LEDs behind the LCD panel, and in premium models the individual LEDs in the grid could be switched on and o independently of the others. The TV would analyse the picture and switch o any LEDs in the grid that were behind where the image was supposed to be black. This was called ‘localised backlighting’ or ‘localised dimming’ or something similar. It’s not as precise as delivering full blacks as OLED (which do it at the pixel level), but it can produce subjectively eective results, with deeper black levels in much of the picture. The parts which the low resolution of the backlight adjustments leave inappropriately lit tend not to be noticed by the human eye, since they are close to areas which are lit. Our eyes are most aected by relative light levels rather than absolute.
Unfortunately, that kind of LED backlighting went out of favour in the quest for thinner and thinner TV panels. To achieve that makers went to edge lighting. At various stages some of them pushed edge lighting as a picture quality enhancement, but it wasn’t. It was all about styling.
Edge lighting works by having the (usually) LEDs around the edges of the screen and then guiding the light as evenly as possible across the whole of the screen. Some models still oer local dimming, but this tends to be more approximate in this arrangement.
Is this a problem? If you always watch TV under room lights, you’ll probably never notice the dierence. If you prefer to watch with the lights dimmed, you’ll probably see some mottling in very dark scenes, especially near the corners.
Another backlight technology that oers improvements is Quantum Dot technology, as used in Samsung’s higher level QLED TVs. In this case, rather than a broad spectrum of backlight, special blue/UV LEDs are used. The light these produce strikes nano-crystals which have been engineered to produce red and green light of wavelengths that achieve an optimal response in the human eye, with reduced leakage into other colours. That increases colour control and eiciency.
Some of Samsung’s premium QLED panels are pushing up towards 2000 nits of brightness. They may not go as dark as OLED, but they go way brighter.
If your main use for your TV is to watch sporting events under room lights with your friends, brighter is definitely better.