Technology Piece on difference between LCD and AMOLED display technologies

Piece for KnowYourMobile Job - 1/11/13

        

I remember when Nokia brought out their first colour screen phone in the distant days of the early 2000s. 

We had street parties.  Finally we could play Snake in colour.

Fast forward ten years and such is the advancement in mobile technology, the unprecedented expansion of what we use our phones for and the exponential rise in popularity and profitability of mobile devices, that fiercely competitive manufacturers ply vast resources into every aspect of construction in order to win consumer loyalty. 

The very nature of touchscreen makes the display screen a vital battleground in this on-going technological war of one-upsmanship.

Traditionally mobile phones have used LCD screens.  This goes way back to the heavy duty bricks of the 90s but they’re still just as popular today with the iPhone 5, HTC One X and LG G2 continuing to use LCD technology.

LCD (Liquid Crystal Display) screens work by way of a fluorescent backlight that sits behind hundreds of thousands of pixels, each one showing different intensities of red, green or blue to filter the light to create all the different colours, and ultimately the image, you see on the screen.  

One of the disadvantages of this is that ‘black’ on an LCD screen will always be a dark grey because what you’re seeing is actually a heavily filtered backlit projection. 

AMOLED, or, if you prefer, Active Matrix Organic Light Emitting Diode (but let’s agree on AMOLED) only started being used for mobile phones screens in 2012.  With AMOLED each pixel on the screen generates its own light.  AMOLED screens therefore require no backlight and don’t have to deal with any of the filters that LCD screens do.  Not only does this make them thinner, it also makes for a wider range of colours, a greater contrast of colour, and a purer, more vivid, light.  LEDs can also simply switch themselves off to create a deeper and truer black.  This has the additional advantage of prolonging battery life if, for example, the phone is on standby or has a black background on the handset.

The HTC One S, Samsung Galaxy S 4 and Nokia Lumia 1020 all use AMOLED displays.

However, and this is where it starts to get tricky, all the content we view on the Internet and on operating systems, both on mobile devices and on desktop computers, is currently based around a colour range called SRGB.

The LCD display’s colour range matches very closely to the SRGB range and so colours tend to look very natural on LCD screens.

AMOLED can display a much larger range of colours than SRGB but, at the moment, the content we view is not as compatible as it is with LCD. 

With no colour management options available, colours on AMOLED displays therefore often look over saturated.  Common theory holds that AMOLED colours, while punchier, actually look less natural.

To confuse the issue further, in the last couple of years, following the good press AMOLED received about the strength of their colour tone, LCD developers like LG tried to match the vivid colours that were in-vogue and seen as big selling points for AMOLED phones, most notably Samsung’s Galaxy range.  LCD developers achieved this by tweaking saturation and gamma calibration on their phones at the development stage to produce more vivid colours on their LCD screens.

The result of this was the colours looked more vivid BUT also lost their natural look.  For example boosting the green might look terrific in Angry Birds but unnaturally vivid in a photograph that requires more variation and subtlety of tone.

If every colour is slightly recalibrated then the entire colour system is thrown off as a result.

Moving away from the technological mumbo jumbo (with a frown and one hand left scratching its head) and on a practical note the very fact that the LCD screen is backlit makes it more readable in sunlight than AMOLED.  This means LCD has a noticeable practical advantage when you’re relaxing by your pool playing Candy Crush before work or sitting in the park trying to watch pornography on your lunch-break (delete as appropriate).

AMOLED screens have also been known to suffer from ‘blue pixel burn in’.  This is your good old fashioned screen burn that occurs when a static image is displayed for a long time.  As blue is the most high energy colour it’s also the most likely to cause a burn.

A lot of the AMOLED vs LCD argument is frankly down to personal preference, but either way Snake is looking a lot healthier nowadays.