Last month I posted about the new wave of UHD (4K) TVs. 4K resolution usually means 3840x2160 and offers four times the pixels of FHD (hence the 4K name). In my post I quoted DisplayMate's Raymond Soneira that said a human being can't really tell the difference between 4K and FHD panel in a 55" TV viewed from a normal viewing distance.
This sparkled a lively debate. Some people say that 4K images are superb to Full-HD ones. Only today Paul Gray, DisplaySearch's director for EU TV research posted his thoughts on the IFA exhibition - and he says 4K provides a completely new way of viewing and enables immersion even better than 3D.
I asked Raymond to respond. So first of all, he says that actual precise measurement of the human eye's sharpness cannot be achieved because the sharphness does not have a "hard limit" - it is a point of strongly diminishing returns. He agrees that under ideal conditions, someone with perfect (20/20) vision will be able to see a small improvement in sharpness above the resolution limit discussed before. But that is under ideal conditions - peak white to pure black pixel-on/pixel-off test patterns viewed in absolute darkness on very high contrast displays.
In real world ambient light viewing conditions the contrast ratio falls significantly, and therefore so does visual sharpness and modulation transfer. You're welcome to read Raymond's ambient light article here. In addition, real TV conent (photos, videos) are inherently fuzzy because the image detail is spread over multiple pixels. So a sharpness difference is even less likely to be detected by a human eye (this is especially true with jpeg images). In movies that are continually changing, a fair amount of image detail is often visually lost due to its transitory nature, plus digital mpeg compression that reduces image detail and sharpness.
So I guess the debate will continue. On one side we have reviewers and consumers saying that image quality is superb. On the other side we have physics saying this is impossible. It may be that UHD content shown in exhibitions and in demonstrations are static images without compression - and these really look better in 4K resolution - especially of course as you tend to look closer at the screen in exhibitions and demos than you'd do back home.
Regarding OLED vs UHD, it seems that this specific competition isn't real. During IFA both Samsung and LG unveiled UHD OLEDs (and Sony and Panasonic's own 4K OLED prototypes were shown earlier this year) and it seems that future OLED panels will indeed support the higher resolution whether it makes sense or not.