Upscaling attempts to utilize higher resolution displays without higher resolution content. In this article, we compare how low resolution, upscaled and native high resolution content appear, along with discussing the motivations behind each solution.
Upscaling uses known pixel values to estimate unknown intermediate pixels. The process works by mathematically guessing or "interpolating" values based on a weighted average of known pixels in the vicinity:
Although not all algorithms yield the same quality, interpolation generally improves otherwise low resolution images. However, attempting to simulate missing pixels comes at a cost; all methods incur some combination of blurring, blocking and halo artifacts:
Unfortunately, any algorithm that reduces one of these artifacts does so at the expense of others. For example, upscaling that reduces jagged edges might induce more blur, and upscaling that reduces halos might appear less sharp. To avoid having any one artifact appear too pronounced, upscaling algorithms therefore balance small amounts of each artifact, such as in the example at the start of this article.
Despite these disadvantages, interpolation is the only option when the original content does not have the necessary resolution. The approach is therefore widespread, and happens when low-resolution photographs are enlarged, when cameras utilize digital as opposed to optical zoom, and when DVD players output low-definition content to high-definition displays.
UPSCALING TO 4K
The current standard for image clarity is 4K. For the first time, this makes individual pixels unperceivable at many common screen sizes and viewing distances giving the viewer a whole new level of realism. However, since content is still catching up with these advances, manufacturers have begun to equip standard 1080P players with 4K upscaling capabilities. While this is definitely an improvement over imagery that has not been upscaled, it still does not compare to true 4K resolution. Just as with DVD players that upscaled their content to 1080P, upscaling noticeably reduces the appearance of blockiness and jagged edges, but falls short when it comes to depicting more detail:
Textures in fabrics, hair and landscapes are all more likely to cross the resolution threshold and become visible, for example. If these images were being compared from digital cameras, it would be the equivalent of going from 2 to over 8 megapixels. Just as an upscaled 2 megapixel print appears dramatically less detailed even at moderate print sizes, so too does 1080P imagery.
Upscaling devices are primarily useful because they ensure backward-compatibility. These devices help make the most of existing movie collections when shown on the latest 4K displays, since imagery will generally appear smoother than it would otherwise. On the other hand, true 4K players are more versatile since they are usually also capable of upscaling their content when necessary.
Upscaling is therefore a stopgap measure when true 4K players or content are not available. Since 4K or "UltraHD" content provides four times the image information and detail as 1080P, the difference can be dramatic, especially when viewed on large screen sizes. These viewing scenarios are becoming increasingly common as television prices continue to drop and technology advances. When true 4K content is available, not needing upscaling is ultimately the only way to achieve the clarity, realism and immersiveness made possible by 4K.