There are many things that one should take into account when deciding if a display or a screen is good or not. One of the factors no matter if we are talking about smart phones, tablets, TVs, or computer monitors is the resolution, which is directly related to the screen's aspect ratio and pixel density. So in order to be able to make an informed choice, we need to understand exactly what those numbers (or abbreviations) mean.
The resolution is a metric that measures how many pixels there are in a particular display. This is in a direct correlation with the amount of content that can be displayed - the more pixels, the more content. The resolution doesn't give us any information about the screen's physical size since the same amount of pixels could be fitted both on a very small display with very small pixels or a very large display with pixels as big as a light bulb. The most common way to denote the resolution is with two numbers in the form (A)x(B) in which the two numbers give us the number of pixels on each side of the display as illustrated on Figure 1.
We can calculate the total number of pixels on a screen by multiplying the two numbers, but people rarely need to do this calculation. Additionally, there are some common resolutions that are denoted by abbreviations, not numbers like HD, VGA, 1080p and so on and we'll discuss what they mean below.
We also mentioned that the display resolution gives us information on the way the pixels are arranged. To be more specific, it gives us information on the correlation between the width and the length (height) of the display. This correlation is called aspect ratio and is usually denoted in the form (x):(y) with x and y being prime numbers. Preserving the information about the aspect ratio is the main reason to denote the resolution with two numbers and not just with the number of pixels. There are a few common aspect ratios and they represent how wide the display is. You can see how the two most common resolutions 4:3 and 16:9 relate to each other on Figure 2. 16:9 is wider because the difference between the sides is bigger.
Pixel Density (ppi)
As we mentioned before, the screen resolution doesn't give us any information about the screen size, so we also don't know how close the pixels of the display are to each other. But both this pieces of information are quite important when evaluating the display quality no matter if it's a mobile device, be it a tablet or a smartphone, or a TV or a monitor. So we have an important metric in this department to help us understand how closely packed the pixels are on a particular display - pixel density. This will also tell us a lot about the image quality, clarity, and readability. The higher the pixel density (the closer the pixels are together), the crisper the image. Pixel density is measured in the intuitive unit pixels per inch (abbreviated ppi). So this is actually an important metric that provides information on the relation between the resolution and the display size. If two screens have the same resolution, but different sizes, the smaller one would have the higher pixel density. If you need to, you can calculate the pixel density by yourself knowing the display's size and resolution.
Standards and specifications
So let's start putting some order into the display resolution world. We will start with the most common aspect ratios and then examples of the most common resolutions discussing the different standards and different use case scenarios and devices.
The most common aspect ratios are 4:3 and 16:9, especially if we are talking not just about displays, but also about video content. Of course there is an abundance of other possibilities like 3:2, 16:10 and 5:3 (sometimes referred to as 15:9) going in between them and 5:4 and 29:16 going to both extremes. But the options are endless and sometimes device manufacturers choose something else that fits their own design. To make things as clear as possible, you can view Figure 3. below, comparing some of the most widespread examples and mentioning their use cases. The biggest diversity of aspect ratios that you'll find is in mobile devices. This is because display choice is very much connected with how the device will be used and the shape and dimensions that the manufacturer wants to give it. With smartphones, the choice usually lies with wider aspect ratios that are used in their portrait side meaning it's actually more logical to call them taller. So 3:2, 16:10 and 16:9 are all common options. With TVs the two main aspect ratios used are 4:3, which is remaining as a bit of a legacy resolution, and the wider 16:9, used by the newer models. Computer (both desktop and laptop) can vary, but with them it's much more common to use 16:10 instead of 16:9 for the widescreen option, which is a bit narrower. In the end, there are all kinds of devices with all kinds of aspect ratios and resolutions, but knowing the standards helps putting it all in context.
When choosing a display with a particular aspect ratio one should take into account what type of content is the display going to be used for so the aspect ratio of the display will fit the content. When a user wants to view a piece of content that has a different aspect ratio from the screen it's displayed on, there are two ways it can be forced to fit. The first option is to stretch the content to the aspect ratio of the screen, but this distorts the image and rarely produces good results. The second option is to display the content in a letter box. This means that the content is displayed in it's proper aspect ratio with black bars in the unused areas of the screen as shown on Figure 4.
When the resolution is annotated by numbers it's pretty easy to determine what is low and what is high, but very often the industry uses abbreviations that they understand, but that might be quite confusing for some users. So let's talk about the most common screen resolutions for mobile different devices and clear the geek lingo in the meantime.
VGA (Video Graphics Array)
VGA was the first video graphics standard to become common and a lot of the new ones are based on it. It was first developed for computer monitors, but nowadays these resolutions are considered as pretty low and even smartphones usually come with resolutions from the higher end of this standard and the newer flagship devices even go beyond.
In the beginning the 4:3 aspect ratio was the base of everything, so the standard VGA resolution of 640x480 has that ratio. Wider versions are also available and are currently increasing in popularity like WVGA (Wide VGA) at 800x480 with a 5:3 (15:9) aspect ratio and FWVGA (Full Wide VGA) at 854 x 480 and 16:9 aspect ratio, expanding only the width of the standard VGA resolution. So VGA is the base and it's used as a base of other lower or higher resolutions. Going into lower resoltuions, this standard resolution can be modified to have half or quarter the pixel count. So we have QVGA (quarter VGA) at 320x240 and HVGA (half VGA) at 480x320. You will notice that the numbers don't need to double for the resolution to double and every time the numbers double the number of pixels quadruples like on Figure 5. The next higher resolution available is SVGA (Super VGA) a.k.a. Ultra VGA (UVGA) having a resolution of 800x600. It also has a wide version WSVGA (1024×576/600).There is also Double VGA (DVGA) which has both multiples of the resolution doubled to reach 960×640. This means it actually has four times the pixel count of VGA. This is the resolution used in Apple's iPhone 4/4S and its famous Retina display.
XGA, QXGA and HXGA
XGA (Extended Graphics Array), QXGA (Quad Extended Graphics Array) and HXGA (Hyper Extended Graphics Array) are all iterations of the VGA standard keeping the same logic, but increasing the resolution. The base resolutions are built with a 4:3 aspect ratio with W used to signify wide versions and +, S (super) and U (ultra) meaing increased resolutions. The resolutions that are part of the XGA are nowadays used for computer monitors and tablets while QXGA might be used in higher end computer monitors only while tablets haven't really reached them yet. HXGA is a standard that is currently being advocated for for ultra high resolution ussages. It's important to note that modern TVs and some of the mobile devices and even computer monitors use the HD (High Definition) standards instead of the VGA variants despite the fact that some resolutions might be very similar. HD will be covered in detail below.
So let's begin with XGA (1024×768) and using variations of XGA+ (1152×864), SXGA (1280×1024), SXGA+ (1400×1050), UXGA (1600×1200) and their respective wide sreen version that you can see in table 2. For QXGA (2048×1536) things progress similarly (table 3.) and so do things for HXGA (4096×3072) (table 4.).
HD (High Definition)
HD is a resolution standard (group of resolutions) that stem from HDTV (High definition TV). The base resolution of HDTV is 1280×720, which has a 16:9 widescreen aspect ratio. When talking about displays especially outside of the TV industry this resolution is referred to as HD or 720p in order to make a clear differentiation from the increased resolution of Full HD or 1080p which has a resolution of 1920×1080. All of the resolutions in this group are quite popular not only in TVs, but also in mobile devices like smartphones and tablets and of course, some computer displays.
Actually all of the high definition resolutions use the 16:9 aspect ratio which makes it a far clearer standard than VGA, XGA and so on. The smallest resolution in this group is nHD which on night (hence the "n") of the Full HD resolution at 640×360. It can be viewed as a building block for the rest since if you put 4 nHD frames in a 2x2 arrangement, you will yeald a resolution of 720p and if you arrange 9 nHD frames in a 3x3 arrangement, you will yeald a resolution of 1080p. Additionally there is qHD (quarter HD) which stands at 960×540.
Additionally, this standard provides options for resolutions that are even higher, which are usually used in high-end TVs, smart TVs and 3D TVs that require very high detail. There is WQHD (wide quad HD) with a resolution of 2560×1440 which is four times the pixel count of 720p. There is 4K UHD (4K Ultra High Definion) with a resolution of 3840×2160 which is 4 times the pixel count of 1080p. The highest resolution possible right now in this standard is 8K UHD (7680×4320) which is 8 times the 1080p resolution as the name suggests. All the resolutions part of the HD standard can be viewed in table 5.
Multiple Resolution Standards Compared Visually
Other useful resources
- How To Calculate A Display's Pixel Density By Yourself
Sometimes you might to know the pixel density of a display in order to evaluate its quality, but the information would simply not be available. You can calculate it yourself if you know the display's size and resolution.
Adebayo Adeolu Ibrahim on November 26, 2013:
Great informative hub
Distant Mind (author) on February 23, 2013:
Thank you for your comment, wilderness. I'm happy the surgery got your eyesight back to normal.
Dan Harmon from Boise, Idaho on February 21, 2013:
When I had cataracts I played with the resolution on my monitor considerably, trying to find something I could read without glasses. Coupled with changing the font size, I finally found a setting, but writers beware! - doing that will change the appearance of your work and won't see what your are writing the same as you do.
After eye surgery I'm back to a normal resolution on the screen, making sure that it matches the screen aspect ratio. I use a large monitor plugged into a laptop, and the monitor doesn't match the laptop ratio, so I have to reset it on the rare occasion I go mobile with the computer if I want it to look right.