Aspect ratio, resolution, PPI, Retina, there are a lot of terms and technologies at play in the world of mobile displays and it can be confusing. Here’s a guide to help you understand what all the terminology means and what you need to consider when buying a phone.
Screen size is measured diagonally from corner to corner. The majority of the most powerful smartphones have progressively moved towards bigger and bigger screens, culminating in a new class of device, starting with the Samsung Galaxy Note - unofficially dubbed the ‘phablet’ (phone/tablet).
When choosing a smartphone; bigger isn’t always better. Large displays are great for viewing more content, while videos and pictures are naturally easier to view, but the larger the screen the more power it requires and battery life can suffer. Devices with large screens are usually thicker and more unwieldy to use.
Unless you’re looking for something specialist like the Note, before you select a phone it’s important to choose a screen size you feel comfortable using. Look for a phone which fits easily in your hand, pocket or bag, with enough space for your fingers to move comfortably around the interface.
With regards to displays, the term resolution is used to express how much detail is on offer when looking at a screen: measured by the number of pixels horizontally and vertically.
Resolution and size aren’t directly linked and you can have a low or high resolution screen, whatever its size. The most important thing to understand is that the bigger the screen, the higher resolution you’ll want in order to have clear, sharp images.
When choosing a smartphone or tablet, there are all manner of quoted resolutions at play usually given a name with the horizontal and vertical pixels in brackets afterwards. The most popular resolutions are:
For a decent image, whatever screen size your smartphone has, don’t choose any a resolution lower than HVGA. and large screens (4-inches plus) should at least have a WVGA resolution.
Recent smartphones shown at CES 2013 from ZTE, Huawei and Sony have HD 1080 resolutions - that’s the same as most modern HDTVs, but on a 5-inch display. You don’t necessarily need that many pixels in a smartphone though - in casual use the majority of people won’t be able to differentiate between a HD 720 or HD 1080 screen.
For a comprehensive list of display resolutions, this Wikipedia article has an useful diagram.
PPI(Pixels Per Inch) is used to measure the number of pixels found within a square inch on a display. This measurement does take into account both resolution and screen size, providing a number relating to the density of the pixels on a screen. The higher the PPI, the better the detail the images and text on a screen should offer.
The first iPhone (2007) featured a 3.5-inch display with an HVGA (320x480) resolution, meaning that it offered 165ppi. The Retina display used on the iPhone 4S (2011) was also 3.5-inches across, but used a resolution of 640x960, offering exactly double the pixel density with 330ppi.
As a rule of thumb, don’t choose a smartphone with a pixel density below 150ppi. Not every manufacturer quotes ppi, but there’s a useful calculator here.
A term you might have heard bandied about with regards to TVs and cinema screens, aspect ratio is the difference between the width and height of a display. It wasn’t until the late 90’s that the average home TV started to move away from a 4:3 aspect ratio and nowadays most video content is shot and broadcast in a 16:9 format.
Most smartphones adhere to a 16:9 aspect ratio so that video playback fills the entire screen, although some deviate slightly for various reasons. The iPhone featured a 3.5-inch display that utilised a 3:2 aspect ratio, meaning most video content had to be letterboxed (black bars at the top and bottom of the video) in order to fit the width of the screen, as it’d been filmed in 16:9. This problem is no longer apparent with the native 16:9 aspect ratio, 4-inch display on the iPhone 5.
One of the most unusual terms associated with screens on smartphones and tablets nowadays is Gorilla Glass, developed by US material manufacturer Corning. Gorilla Glass and now Gorilla Glass 2 are used for their amazing resilience - Gorilla Glass can withstand being tapped, scratched, dropped and impacted.
Retina is a term trademarked by Apple. The term ‘Retina’ is used with any of its high resolution screens when the pixel density is high enough that the user can’t distinguish individual pixels when holding the device at what a normal distance from the eye. The first Retina iPhone was the iPhone 4.
The two leading display types in devices like tablets and smartphones are LCD and LED-based technologies commonly called AMOLED.
LCD means Liquid Crystal Display. LCD’s are often chosen for their sunlight legibility, vivid colours and excellent whites, however they typically use more power than LED-based technology.
There are many types of LCD and as the technology has evolved, there have been more variations, most recently S LCDs (Super Liquid Crystal Displays). Some companies also brand their displays to make them sound more appealing and unique: Sony’s Reality Display, Apple’s Retina Display and LG’s TRU HD display all in fact LCD variants.
LCD screens can utilise IPS (In-Plane Switching) technology. IPS technology is said to improve responsiveness, colour reproduction and viewing angles.
AMOLED stands for Active-Matrix Organic Light-Emitting Diode and whilst LCD screens have an advantage when it comes to reproducing whites, the blacks on an AMOLED display are second to none.
AMOLED screens are also known for their more efficient power usage (resulting in a longer lasting battery) and excellent contrast ratio, but can struggle with sunlight legibility and have a tendency to display everything with a slight blue hue.
AMOLED technology is expensive, it’s usually reserved for high-end smartphones - to save costs HTC swapped from AMOLED to LCD technology during production of the HTC Desire.
Like LCD, as AMOLED technology has developed there have been more variations. The Motorola RAZR i uses Super AMOLED Advanced technology and the Samsung Galaxy S3 uses HD Super AMOLED Plus technology.
Read more in-depth information about the differences between LCD and AMOLED technology here.
Often manufacturers develop proprietary technology unique to their phones. Some examples include:
BRAVIA Engine - Sony’s Mobile BRAVIA Engine and now Mobile BRAVIA Engine 2 have been used on a number of it’s leading smartphones for the past two years, using technology found in Sony’s TV range. The Mobile BRAVIA Engine software uses software algorithms to improve contrast, colour management, image noise and improve sharpness over the same type of display without the BRAVIA Engine.
PureMotion HD+ - The PureMotion HD+ technology found in the Nokia Lumia 920 ensures even when you're swiping through apps, homescreens, pictures or web pages insanely fast, everything stays crisp and clear. PureMotion HD+ incorporates the display’s ability to detect touch input, even when the user is wearing gloves.
Does having the highest PPI matter to you? Do you prefer the larger screens currently being released in the market or do you think anything over 4" is too much? Tell us your thoughts in the comments?
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