The highest display resolution of the 40UA6406 is 4K Ultra HD. That's over four times the display resolution of a Full HD television, which is the most frequently found display resolution. 4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
This TV's display resolution (4K Ultra HD) is in fact the best display resolution amongst all mid-size TVs that have been on the market for a similar time to the 40UA6406.
Amongst similar types of TV the worst display resolution is HD Ready.
4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
It may also be worth considering one of the other 4K Ultra HD TVs currently available including the LG 40UF695 (£349.00) which is cheaper.