تفاوت صفحه نمايش هاي AMOLED و LCD

AMOLED vs LCD – What is the difference?

Display technology is often a key battleground when it comes to top of the line handsets. But it’s not just display resolution and screen size that you’ll find on a spec sheet, manufactures also list different display types to choose between as well. Often you’ll find that manufactures stick to a particular display type, such as Samsung with its AMOLED technology or HTC opting for LCD, citing certain benefits over the competitions’ technology.

So let’s find out if really there’s a noticeable difference between these two displays technologies, if there is what sort of differences we can expect, and if the company marketing hype is to be believed.
The technology

First things first, let’s quickly go over the technological differences between the two display types before we delve into how this affects the consumer experience.

We’ll start with LCD, which stands for Liquid Crystal Display. The properties of this liquid crystal are a little complicated, but the important thing to know is that liquid crystals untwist when an electric charge is applied to them, which affects the frequency of the light transmitted through it. Combine this will two polarized panels and you can control the flow of light by twisting and untwisting the crystal molecules.

However, these liquid crystal materials don’t emit any light of their own, so a backlight is used behind the filter layer in order to generate light. A grid of integrated circuits is then used to control each pixel, by sending a charge down into a specific row or column. Colors are created by the use of red, green, and blue filters, known as sub pixels, which are then blended by varying degrees to produce different colors.
The construction of a red LCD pixel.

The construction of a red LCD pixel.

AMOLED, on the other hand, uses lots of tiny colored light emitting diodes (LEDs) to produce light and different colors, which sounds quite a bit simpler. By adjusting the voltage, and therefore the brightness, of each of these red, green, and blue LEDs you can create a wide range of colors, or lack of colors (blacks).
The showdown

The most noticeable difference between these two screen types is the range of colors that can be displayed. The available colors that can be displayed are known as the color gamut, which is a portion of all colors that can be seen by the human eye.

Most types of media fit into the standard RBG color gamut, which most LCD screens aim to match. This is often why LCD screens are considered to be the most natural, but that’s simply because it most closely matches the color range used by other sorts of media. AMOLED displays offer a much larger gamut than LCDs, which can cause images to look much more vibrant.

The reason for the large differences lies in the way that these technologies work. Because LEDs can be individually controlled to a much greater extent, and development isn’t so concerned with the quality of filters as is the case with LCD, it allows the display to produce a wider gamut due to superior blending of primary colors. Another benefit of AMOLED is the greater control over blacks, which is achieved by dimming or turning off individual LEDs.
Galaxy S4 vs HTC One gamut comparison

A gamut comparison between the Galaxy S4′s AMOLED display and the HTC One’s LCD display. The curved shape represents the visible spectrum, the black triangle is the sRGB gamut, and the white line is each display’s gamut. Notice the additional greens and blues with the S4.

However, a wider range of colours isn’t always better, as it can lead to images look oversaturated and can cause pictures to end up looking a tad distorted in extreme cases.

The strange thing here though is that LCD manufactures often aren’t satisfied with the look of their displays. In an attempt to make their displays look more vibrant, possibly just to keep up with the marketing of AMOLED displays, some LCD device manufactures often mess around with the levels of saturation, which can also end up ruining the color balance. If you’re looking for vibrant colors, then you’re probably better off with an AMOLED display with a decent colour balance, rather than an oversaturated LCD display. If you’re interested in a closer look at AMOLED/LCD saturation, then I highly recommend this video by Erica Griffin.

But it’s not all bad news for AMOLED displays, the technology does have some advantages over LCD. For a start the viewing angle tends to be a bit wider, as light can only travel through the LCDs crystal molecules and polarized panels at a limited angle, although this does vary from handset to handset. LEDs also react faster to changes in voltage than crystal molecules, which means that response times are often faster on AMOLED displays too.

One final point to consider is power consumption. As LCD displays are constantly powered by a backlight they tend to draw more power than OLED based displays, which can turn off LEDs when displaying darker images. However, different colored LEDs have different levels of power consumption, so energy draw is more consistent and predictable when used LCD technology.
Different colored PHOLEDs have unique levels of efficiency and operating lifetimes.

This chart shows the lifespan of different colored PHOLEDs. Although the technology is a little different to AMOLED, the difference in colour lifespans is typical of all LED based displays.

The different LED energy levels can also shorten the lifespan of the displays. The blue pixels in LED displays require the most energy to power, but that also means that they can burn out faster. After a long time this can result in a slight tinting over part or all of an AMOLED display.
So which display wins

I know it’s a cop out, and you might here this a lot, but in the end it really is down to personal preference. Even within the same display types there are varying levels of saturation, gamut, and differences in calibration, so picking the best display type for yourself isn’t really an exact science. You could like HTC’s LCD displays but absolutely hate the look of LG’s. Typically, those looking for more vibrant displays will be better off with AMOLED, but well built and properly calibrated LCDs may provide a more realistic look.

On top of that, each technology has its own advantages and disadvantages that are also worth considering. If you’re looking for a long lasting display then you might be better off with LCD to avoid pixel degradation, whilst consumers looking for a better battery life and a wide range of colors could be better off with AMOLED.