What I admire most about the television industry is that the builders kept it simple.
Let’s walk down memory lane for a minute. TV began in the 1950’s. Colour pictures came along in the 1960’s. Stereo sound appeared in the 1980’s. Through all of this evolution the only decision you had to make was what size you wanted the screen to be.
Well that started to change by the early 2000’s. With the wide scale availability of “Flat Panel” sets a few new technologies began to appear. LCD, Plasma, DLP, Projection … All had their strengths and weaknesses. Suddenly you had decisions to make and they weren’t easy.
Now we’re at the end of the 2010’s and things have settled down to a large degree. There are really only 2 competing technologies left. LED and OLED. What’s the difference you ask? Let’s go for a drive…
LED TV’s are not really new. It’s really just an LCD display which has been in widespread use in consumer electronics since the 1990’s. The LED part really only pertains to one component of the display. It’s backlight.
I’m not going to go into a deep dive on how LCD works. You can Google that. What we need to understand for our purposes is relatively simple. LCD’s work by passing light through liquid crystals pressed against a polarizing filter.
The LED in an LED TV is simply the source of white light that passes through those crystals. In an older LCD TV the white light was made from compact florescent tubes. Just like the ones over your head in your office, only much smaller. In an LED TV rows of white LEDs are used in place of the CFL tubes.
The colour that you see on an LED TV is the result of electric current passing through the crystals and causing them to rotate against the polarizing filter. This makes them visible.
OLED or Organic Light Emitting Diode is something much newer. It uses material that when exposed to electricity produces it’s own white light. Colour is added by tinting a second layer of material in front of the light source.
Once again I am simplifying here so that you don’t fall asleep. The key take away is that each individual pixel on the screen lights up on it’s own. There is no single white light source. When you seen black on an OLED TV you are seeing no light at all.
This is really the key difference between the two technologies. One thing. Black.
An LED TV makes black by turning off all of the colour crystals. But you still have the white light from the backlight. This never goes away. So when you see black what you are seeing is the polarizing filter blocking all of the white light from the LED reaching the screen. The quality of the black you see is limited by the quality of the polarizing filter. Even in top quality sets you will get some light leakage. Usually at the edges of the screen or in the corners. This often makes blacks look more like dark grey.
If you want to see this for yourself… Turn on an LCD computer monitor, with nothing attached to it, in dark room. As it powers up you usually see just a black screen. See that Dark blueish tint? That’s the backlight and polarizer working together.
OLED’s make black by turning off their individual light source. This makes for a much darker black since you don’t have the constant white light source to contend with.
For the photographers in the room you know where I’m going. If you can get white and black right then all of the other colours in an image fall inline perfectly. This is the biggest factor in why OLED screens look so beautiful in person.
It’s not all wine and roses though. We’ll talk about OLEDs downsides tomorrow.
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