In my last post I talked about the increasing popularity of devices with high pixel density screens such as Apple’s Retina Display. Now I’d like to go into a bit more technical detail and consider what makes such a screen look so good, considering a little bit of the past, present and future on the screens we most commonly see.
There are 3 aspects of a high PPI screen – resolution, physical size and viewing distance.
Screen resolution is measured in pixels (the tiny dots that make up the image on your screen), giving the number of pixels on the horizontal and vertical axes of a screen. Multiply these values and you have the total number of pixels on the screen. For example, a typical laptop has a resolution of 1366 x 768, which gives a total pixel count of 1,049,088 – over a million pixels. Pixel count has no bearing on physical size – pixels can be created at any size allowed by technology, meaning many current smartphones have the same resolution or greater than a 50 inch HD TV.
The physical size of screens is an interesting topic. In the UK, screens are always measured on the diagonal and always in inches, bizarrely. Until fairly recently we saw a trend of ever-increasing mobile phone screen sizes; indeed they still creep up with every new iteration, but we’ve reached (and in some places surpassed) the ideal device size. I have a 2 year old Samsung Galaxy S3 and it only just fits in my pocket when I sit down. Some of this year’s top spec Sony phones could be used as tribal hunting weapons.
So mobile phone screen sizes have plateaued at a maximum of about 5 inches on the diagonal. Tablet screens are also limited by device size and weight, coming in 3 distinct size categories ranging between approximately 7 and 10 inches. Phone/tablet crossovers also exist, like the Samsung Galaxy Note range, but I personally refuse to call anything over 5 inches a phone. If it doesn’t fit in my jeans then it’s a tablet.
I digress. Laptops have a huge variety of screen sizes, from the smallest netbooks with 7 inch screens to tap out screenplays in cafés to 19 inch gaming behemoths that weigh as much as a large dog and set fire to your knees. Desktop monitors have a similarly wide range, with manufacturers recently upping the size race again to the latest resolution buzzword, 4K. More about that later, but consumer desktop screens are most commonly LCD panels in widescreen (16:9 or 16:10) format these days, ranging from 19 to 30 inches.
This brings us to TVs, which conveniently start at about 19 inches, the same size as the smallest monitors, but extend to about 70 inches, or an entire wall of your lounge, whichever is smaller. Yet currently almost all TVs have a resolution of just 1920 x 1080, otherwise known as (full) HD.
Fun fact: The best cinema seats are 1.5 times the height of the screen away from the screen with a viewing angle of 37 degrees (source).
The difference between TVs and monitors (and indeed all devices) is all about the viewing distance. When you look at your phone, you’ll hold it fairly close to your face. You’re close enough to the screen that on a low PPI device you can see individual pixels. When you watch TV you’re sitting across the room, meaning much larger pixels are acceptable without a noticeable quality problem. The same goes for a cinema. Yes it’s a huge screen, but unless you’re in the front row you’re actually quite a long way away from it.
Test yourself: Use your fingers in front of your face to make a box surrounding your TV screen. Is it much different from the size of your phone? Try it next time you go to the cinema too.
The future’s coming (quick, hide!)
We’ve become used to HD displays very quickly (we had standard definition TV for years and years – HD has been around for 5 minutes in comparison), and despite the fact that they still look great we’re a greedy bunch and we want more – bigger, better and yesterday, please.
The next big thing in screen sizes is 4K, otherwise known as UltraHD. 4K has been around for quite a while; the vast majority of UK cinemas have either 2K or 4K digital projection. Consumer 4K (to be found in TVs and computer monitors) is in itself a slight misnomer (and a bit of a swizz if you ask me) as the 4K refers to the horizontal measurement, i.e. 4000 pixels wide, when the 1080p/I naming convention with HD refers to the vertical measurement. Then there’s the actual resolution of 3840 × 2160, less than 4000 on the horizontal. Having said all that, there’s still 8,294,400 pixels to look at, which is a fair few in anyone’s book and 4 times as many as HD. Then there’s 8K (otherwise known as Super Mega Ultra Wicked HD) just around the corner…
Those of us with high PPI digital devices are now enjoying a level of sharpness more akin to print. Perhaps it won’t be long before the 72 PPI ‘for screen’ standard is completely dropped and everything is designed to a minimum of 300 PPI. We’ll all need a faster internet connection in order to cope but it could be a similarly magical shift to the one we had not too long ago from analogue standard definition (SD) to full high definition (HD) television. You could argue it’s already happening.