LCDs vs OLEDs

[Carl Fredrik Ahl]

Hi,

I know how LCDs and OLEDs works. LCDs uses a backlight and liquid crystals to control how much light is passed through the color filters. In OLEDs all pixels lights up by them selfe. Now, I wonder a few things:

1. Why can't LCDs be completely dark? I know that the backlight is on all the time, but the polarizers can align so that no light can come through?

2. Why does OLEDs have better contrast? Is it because it can get completely dark? LCDs can still get brighter. 

3.  Why does OLEDs have better viewing angle than LCDs?

[MigL]

You essentially answered your own questions.
Think of the liquid crystals as 'shutters' which allow light to pass through or not.
And just as shutters always leak a little light, no polarizer is 100% effective.
Some light always leaks through, and 'blacks' aren't really black.

In OLEDs ( or plasma displays ) the pixels themselves emit the light, and are either on or off.
And when they are off 'blacks' are black, giving better contrast.

The fact that the pixels also radiate in all directions, instead of the LCD/LED case, where the backlight passes through a crystal 'window', means that the viewing angle is not reduced by the 'window'.

Black 'blacks', high contrast and viewing angle are what makes for a good TV.
For watching TV movies, high refresh rate plasma displays used to be the favorite.
Now they are being replaced by OLEDs with HDR ( more important than 4K ) for the best contrast.
For computer screens LED is perfectly adequate.

[Externet]

1.- The individual LCD shutters are not fully opaque, and are surrounded by boundary gaps -as lines between tiles-  that cumulatively leak noticeable backlight, even when made very narrow.

2.- Because there is no backlight-always-on condition.

3.- Liquid crystal shutters twist to direct (funnel)  the light normal to screen plus the comment above; Oled emitters are wider angle light emitters. Like opening a window blind compared to a lamp.

[Moreno]

I've read some critical opinions about OLED screens, that colors they depict are too unnatural and hence LCDs are much better. I wish to know more opinions on that subject. Also how QLEDs compare to both OLEDs and LCD in terms of quality?

[StringJunky]

29 minutes ago, Moreno said:

I've read some critical opinions about OLED screens, that colors they depict are too unnatural and hence LCDs are much better. I wish to know more opinions on that subject. Also how QLEDs compare to both OLEDs and LCD in terms of quality?

What does it matter? It's all shit however you colour it.