VPL-VW600ES 4K and Sharpness Demonstration
Above in the first photo player, you'll find both 1080p and 4K photo pairs. One is basically uncropped, the other far more so. Remember, that even if you expand our images they are only 1000 pixels wide, barely half of a 1080p image. That's why the close ups.
With 4K content, even the highly cropped image isn't showing the content at full resolution. That said, you can tell the difference between 1080p and 4K content, all of which is more detailed than any less expensive projector.
The one exception to that is the last pair (Bellatrix from Harry Potter), where the close-up is a very small area of her outfit, perhaps only 1 or 2% of the whole projected frame. Look at the close-up of that one, and then move back and you'll barely be able to spot the material detail that you were just looking at.