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The Eye & The Science of Colour: Galaxy S III PenTile Display Explained

grand master

 

 

The Eye.jpgThe eye is arguably the most important of our five senses and the one that we rely on the most in our everyday lives. Having evolved over a period of 600 million years, our eyes are incredible instruments that could one second be reading text off a computer screen in front of us whilst the next second be exploring the night sky and the cosmos – detecting the faint light from distant stars and galaxies: light that was emitted billions of years ago. With the amazing science that lies behind how our eyes work and how we see things, it’s no wonder that a huge amount of research has been performed on how to design better mobile phone displays that work hand in hand with how we see.

 

In this article, we explore how the eye perceives colour and how colour is produced on mobile phone displays. We’ll then go on to compare and contrast how different phones create colour and look at how the design of our eyes informs the design of mobile phone displays. In particular, we’ll look at the PenTile display on the Samsung Galaxy S III, explore why it’s taken such a beating in the tech press and ask whether it's deserved.

 

Rods and Cones

 

Eye.jpgOur eyes contain two types of light receptors: “rods” and “cones”. Rods are highly sensitive to the brightness or intensity of light - the typical human eye features 120 million rods which are spread out across the retina – most of them placed away from the central retina. Cones are less numerous on the retina: they’re packed together towards the centre of the retina and they’re less sensitive to light than rods are. The 6 million cones on our retina are able to distinguish between different shades and different colours of light.

 

Using a combination of rods and cones, our eyes are able to give us great vision regardless of the time of day and the light level. During the day, cones and rods work together: rods provide basic vision whilst cones allow us to distinguish between different colours. At night, when is it much darker, we retain the ability to see using rods, albeit without the cone-provided ability to distinguish between different colours.

 

Forming Colour: Red, Green and Blue

 

RGB Colour.jpgThe human eye features 3 types of light-sensitive cones – each type of cone is sensitive to a different colour. The brain combines the electrical signals from “red” cones, “green” cones and “blue” cones to calculate the colour of what you’re looking at.

 

All of the colours that we perceive on a daily basis can be broken down into different proportions of red, green and blue. Combining these three colours in certain ways can create any other colour: for example the combination of blue and green makes cyan, the combination of red and green makes yellow and the combination of blue and red makes magenta. Combining red, green and blue together at the same time in equal proportions creates white light.

 

Creating Colour: RGB Colour Displays

 

The first mobile phone with a colour display was the Sony Ericsson T68i. Released in 2001, the T68i featured a 101x80 resolution screen with the ability to show 256 different colours. More than 10 years on, almost every single mobile phone in the world now features a colour display with many smartphones now having high-resolution displays that can rival those found even on televisions.

 

RGB Stripe.jpgThe latest smartphones such as the Samsung Galaxy S III, the HTC One X and the Galaxy Nexus feature high-resolution 720p displays (a resolution of 1280x720 pixels) and the ability to show up to 16 million different colours. Typically, each pixel or “picture element” on a smartphone display is formed from three sub-pixels: one red, one green and one blue. As discussed above, it is possible to create any other colour from a combination of these three colours. Mobile phone displays make use of this fact: by forming a picture element from three coloured sub-pixels, it is possible to create any desired colour on the display simply by controlling the brightness of each sub-pixel.

 

High-end handsets such as the HTC One X now pack more than 2.7 million sub-pixels into a pocket-sized 4.7-inch display: this is how they can create their super-sharp and realistic colour images. That’s a ton of sub-pixels, each updating themselves dozens of times every second simply to bring you a rich multimedia experience on your smartphone. Amazing stuff.

 

PenTile Displays & Galaxy S III: Another Way to Create Colour

 

RGBG PenTile.jpgThe Samsung Galaxy S III caused controversy online and complaints from various technology sites including The Verge when it was announced that it would feature a display with a “PenTile” RGBG sub-pixel matrix. Whereas a pixel in a traditional colour display is formed from three sub-pixels (red, green and blue), a pixel in a PenTile display is formed of only two sub-pixels. Sub-pixels are laid out in alternating rows of red-green-blue-green (RGBG) with green sub-pixels essentially being “shared” by two neighbouring pixels. Clever computer algorithms are then used to adjust the brightness of each sub-pixel to ensure that the correct colour is displayed.

 

Proponents of PenTile point out that the cones in our eyes are more sensitive to green than they are to either red or blue. Indeed, with many things in nature such as grass, plants and trees being green, our eyes have evolved over time to become more sensitive to green light. This comparative sensitivity of the human eye to green light suggests that by focussing on providing a larger number of green sub-pixels than those of other colours, the perceived quality of a picture can be improved. This is the approach that Samsung have followed with the use of PenTile technology on the Galaxy S III.

 


Eye Sensitivity.jpg
The sensitivity of the human eye to different colours (Wikipedia). The human eye’s vision system is more sensitive to green light than red light or blue light. The standard formula for brightness/luminosity is Luminosity = 0.3 R + 0.59 G + 0.11 B where R, G, B are the red, green and blue components.

 

Many smartphones with organic LED displays make use of the PenTile RGBG sub-pixel matrix rather than a full RGB sub-pixel matrix. This is because blue organic LEDs have comparatively shorter lifetimes than red and green organic LEDs. Reducing the number of blue organic LEDs can make displays easier to manufacture and can also increase their lifetimes. Criticisms of PenTile include jagged edges on some straight lines – particularly on low resolution screens. For the most part, this is incredibly difficult to notice on a high-resolution 720p display so the downsides of PenTile could be limited in the most recent handsets.   

Handset Top.jpg 

Phone

Resolution

Sub-Pixel Matrix

Apple iPhone 3G S

320x480

RGB

Apple iPhone 4

640x960

RGB

Apple iPhone 4S

640x960

RGB

BlackBerry Bold 9900

640x480

RGB

HTC One X

1280x720

RGB

Nokia Lumia 800

800x480

PenTile RGBG

Nokia Lumia 900

800x480

RGB

Samsung Galaxy Nexus

1280x720

PenTile RGBG

Samsung Galaxy Note

1280x800

PenTile RGBG

Samsung Galaxy S

800x480

PenTile RGBG

Samsung Galaxy S II

800x480

RGB

Samsung Galaxy S III

1280x720

PenTile RGBG

 

Other variants of PenTile technology include the RGBW PenTile matrix. Designed for use with LCD displays, RGBW PenTile features an additional white sub-pixel to increase the brightness of the display and to improve outdoor visibility.

 

Your Thoughts…

 

In this article, we looked at how the rods and cones in your eye work together to allow you to perceive the wonders of the world. We discussed the role of cones in helping you to perceive colour and looked at how mobile phone displays make use of this fact to present vibrant and realistic images in the palm of your hand. Finally, we looked at how the Samsung Galaxy S III caused controversy with its use of a PenTile matrix and looked at what that really means for you as the consumer.

 

What are your thoughts on the Galaxy S III’s display? Do you prefer an RGB display (such as the one found on the HTC One X) or a PenTile display (such as the one found on the Galaxy S III)?  If you could build your own perfect smartphone, would you use PenTile technology? We’d love to hear your thoughts and views – please do drop us a comment below!

 

Ken Lo writes about mobile technology and the mobile industry at Ken's Tech Tips.

14 Comments
I lile the sg3 and nice blog lots of info!
newcomer

Hello Team is anyone know how to set Samsung galaxy S111 to access internet withh giffgaff sim card?

 

Thanks

 

augur

sukumas, this isn't the place to post your question. However, if you look in the main forum you will see detailed information on setting up the S3 for internet/MMS

apprentice
1st Smiley Very Happy
apprentice
ohwell 2nd , i like pentile because green is good for the eyes
giffgaff; ergo sum

@OP Fantastic blog

 

@kullyxo Actually it has been scientifically proven that Blue colour is the most pleasent for the eyes.

top cat
At my most recent executive health screening I discovered I was a bit colour blind - I must have slightly faulty cones Smiley Surprised
rocket scientist
interesting read
pathfinder

Nice interesting read.

seer

 

Thanks for the blog Ken.  Very informative.

 

[Edited to remove reference to religious debate which is being removed.]