The technical development of TVs has come a long way since the start of the century. Back in 2000, Cathode ray tubes (CRTs) were still standing. Around 2005, rear-projection TVs became popular as they allowed much larger screen sizes. These were followed a few years later by plasma displays, LCD, and LED screens. Even large TVs have now dropped in price so much that screens of 55 inches and above are within most people’s budget.
But is a bigger screen size better? What factors should influence the decision of what size TV screen is best?
While budget and space restrictions will play an important role in deciding, there are ways to determine the optimum TV screen size as a comparison site Kagoo points out. A TV screen will fill a certain amount of the viewer’s field of vision. The bigger the screen and the closer the viewer sits to the screen, the larger the viewing angle will become. The higher the viewing angle, the less the viewer will see the edges of their field of vision feel more immersed in the scene. A similar effect is used in cinemas. An IMAX screen covers a much more significant part of the viewer’s field of vision and provides a more ‘immersive’ viewing experience than a traditional cinema screen.
This is why THX recommends a viewing angle of 40 degrees for an immersive viewing experience. This means, if the viewer sits 9 feet away from the TV, the screen would have a 90-inch screen diagonal to achieve a 40-degree viewing angle. This seems vast compared to the size of TV most people are used to, but many consumers have pointed out that it is surprisingly easy to get used to a large screen, and many wish they had bought an even larger one.
The Society of Motion Picture and Television Engineers (SMPTE) recommends a viewing angle of 30 degrees, which is quite a bit less than THX’s recommendation. It would still require a 68-inch screen when sitting 9 feet away. Bigger seems to be better when following these recommendations!
But the level of immersion is not the only factor to consider. Ultra-high-resolution screens such as 4K UHD with a resolution of 3840×2160 pixels or 8K UHD (7680×4320 pixels) have become more affordable over the last two years. So most people will wonder when an ultra-high resolution screen makes sense and when a cheaper Full HD (1920×1080 pixels) or even 1280×720 pixels HD screen is sufficient.
The big brands such as Samsung, Panasonic, and LG are marketing 4K UHD TVs as a ‘must-have.’ Is this justified or just another sales strategy?
The key to answering these questions lies in the native resolution of the human eye. The clarity of vision is also referred to as visual acuity and is limited. There is only so much detail someone with 20/20 vision can see. Although the exact value depends on several different factors, such as the contrast between elements, 60 pixels per degree is seen as an accepted value.
When sitting in front of a TV, the screen’s pixels will cover a certain angle of the viewer’s vision. When moving closer to the TV, the same amount of pixels will now include a wider angle, which means the number of pixels per degree is reduced, and individual pixels will be easier to see the closer one moves to the TV. When moving further away from the screen, the opposite is true until the number of pixels per inch exceeds 60. At that point, the human eye cannot differentiate between individual pixels, and moving further away will not increase clarity; it will only make the screen appear smaller.
The chart below shows the connection between screen size, resolution, and viewing distance. Thicker lines represent optimum viewing distances for 4K Ultra HD TV, 1080p Full HD, 720p HD, and 480p resolutions.
For example, a 55-inch Full HD TV is best viewed from 7 feet away. The optimum number of 60 pixels/degree is achieved at that point, and the picture appears as sharp as possible. Moving closer would make the picture look blurry or pixelated, and moving further back would make the TV screen appear smaller without any improvement of image quality.
The chart also shows the viewing angles recommended by THX and SMPTE. It is interesting to see that the 1080p recommended viewing angle and the SMPTE recommended angle are very close. This would probably provide a good starting point when choosing a TV: sitting close enough to give an excellent experience without requiring a more expensive 4K UHD TV.
So when does a 4K Ultra-HD TV make sense? For most people sitting at a comfortable distance away from the TV, a 4K-resolution screen is unnecessary. It only makes sense when sitting very close to the TV to achieve a fully immersive experience similar to an IMAX cinema. When choosing a huge screen, such as an 80 or even 100-inch TV, the higher resolution will have advantages, as the image is a lot larger.
The limited amount of 4K content available should also be taken into account, but this will increase in the future. YouTube, Netflix, Amazon Prime Instant, and other streaming services have started to offer 4K content, although the number of movies and TV shows on offer will disappoint most people. 4K Blu-ray Discs are expected to be available towards the end of 2015.
I’ve seen a chart like this a long time ago but this one seems more detailed. I wasn’t aware that 4K isn’t actually that useful.