Originally Posted by Doug Blackburn
I also question their statement that 2160p has 4 times the clarity of HD video... 4 times the pixels, yes. 4 times the clarity? I don't think so and I have no idea how you would ever quantify such a statement anyway. Not many would argue that HD is "clearer" than SD, but the number of pixels is about 5.9 times greater for HD vs SD. Would anybody ever say HD has 5.9 times more clarity than SD? I don't think so since there are no measures of "clarity". Resolution does not equal clarity, there are many other variables.
what if they used the term sharpness instead?
Sharpness is the quality of an image that gives it clearly defined boundaries. This should not be confused with the type of artificial sharpening that you often see in poor DVD transfers an excessive use of the sharpness control on the display. These only result in ringing and edge enhancement, which makes the image worse instead of better. A good example of sharpness can be had by comparing a good plasma or LCD display with a good CRT. CRTs can look very nice, but they simply cannot complete with the sharpness of a plasma or LCD.
Clarity is the quality of an image that appears when the image is free of artifacts. These artifacts come in a wide variety of types and for a wide variety of reasons. They include: poor focus, poor geometry, poor convergence, chromatic aberration, ringing, moire, line twitter, and interference/ghosting/snow (for over-the-air broadcast).
Problems with image clarity are result of the quality of the optics, processing, or mechanical alignment, and involve the display adding something to the image that is not originally there. Problems with sharpness can be influenced by the resolution, optics, and other inherent properties of the display device, and involve the display removing from the image something that was originally there.
The importance of these two factors is perhaps best illustrated by thinking back to the first time you saw a good plasma display fed by a good source. Compared to CRT images, plasmas could produce an image with startling clarity and sharpness that results in an almost scary looking-though-a-window quality that CRTs simply cannot match. The important fact to note for this discussion is that these relatively early plasma displays offered lower resolution, much lower contrast, and often worse color accuracy than the CRTs of the day and they still could look better, sometimes much better.