|Was wondering, what resolution would the human eye be capable of?...2160i? 4320i?
Don't have a ready answer, but recall some snippets from various threads that are indirectly relevant. This range of vertical resolutions, assuming an equivalent or greater range of horizontal resolution, is typical of some JVC D-ILA
panels for projectors that been demonstrated or are under development. They're aimed initially at theater and industrial use. Such projector systems, with no moving parts except for hard-disc drives, can put such high resolutions on screens.
By contrast, although the initial negatives shot for movies may have resolutions matching or exceeding these numbers, copies made for mass distribution sharply cut resolution. Then, when this reduced-resolution film is run through theater projectors, the mechanical 'jitter' further diminishes resolution. Details on screen may actually be worse than the best HDTV available in homes.
Also, for about $20k, IBM will sell you a LCD monitor with such exceptional 9+ megapixel resolution. They just got an award for the display, described here
(about 1/3 down, or search for "Model T220.") It's meant for commercial/industrial use, such as displaying photos. And someone in the CRT forum recently mentioned routinely working with such resolutions related to X-ray images. -- John