If you attended or read about this year’s Consumer Electronics Show it was hard to escape the hype about the new high resolution televisions. 4K! 8K! Unbelievable amounts of K! But how much display resolution does one actually need?
The short answer: it all depends on viewing distance from the screen.
The long answer: resolution is one of several factors that needs to be considered together when evaluating capture, post production and display technology. In much the way signal-to-noise ratio, frequency response and distortion are always looked at together when evaluating audio systems, resolution needs to be considered along with many other factors when evaluating image systems including: dynamic range, contrast, brightness, color gamut and frame rate. My friend Mark Schubin gave an excellent (as always) presentation about this in November, 2014 which is pasted below.
The research WCI did for the large scale immersive films the Doha Film Institute is creating showed that the key driver of how much resolution is enough is viewing distance from the screen. To wit, if you’re thinking about replacing your 50 inch TV with a 4K model and your couch is 150 inches back from the screen don’t bother. You won’t be able to perceive the difference in resolution. However, increasing the dynamic range of the image, as Dolby is proposing, increasing the contrast and the brightness of the display will have a very, very noticeable effect and will yield greater benefits than increasing resolution.
On the other hand, at very close distances, e.g., less than one screen height away, resolution does become critical. Continuing the above example, if you like to watch your 50 inch TV from 40 inches away a 4K set will indeed change your life, although probably not as much as a new pair of glasses.
An unexpected corollary to this was that at very short viewing distances display resolution is actually more important than source resolution. We compared 2K and 4K projection screens viewed from ½ screen height distances with both 2K and 4K source material. What we found was that the perceived quality improvement going from a 2K to a 4K projector with 2K source material on both was greater than the perceived increase in a 4K projector with 2K source material to the same 4K projector with 4K source material.
Looking beyond display, there are, obviously, other reasons for capturing and posting at high resolution. Generally speaking, more resolution means more flexibility, e.g., the ability to zoom and reposition and image in post, the ability to add stabilization, the ability to reproduce material, etc. But this is not free. Data space and processing time increase exponentially with resolution. So if one is creating a webisode for YouTube perhaps it best not to shoot 100 hours of 6K Red Dragon files.