>> monitor.

>Unless it�s a bigger one.

Unless its two times bigger or more.

...Well that's based on my extrapolation of data from this graph on this webpage...

If you watch a 30 inch 1080/HD TV at 1.2 meters, then its worthwhile watching a 30 inch 4K/TV at a distance of between 0.6m and 1.2m in order to receive the benefit of 4K/HD over 1080/HD.

Alternatively, fixed at 1.2m from the screen, then watching 4K TV's in the range from 30 inch through to a 60 inch is worthwhile compared to watching a 30 inch 1080/HD TV at 1.2m

Thus, as a rough guide, it is not until the diagonal screen size at least doubles with a 4K TV, that you should consider sitting further from the screen than you would with a 1080/HD TV.

Also see the chart that they provide on optimal distance. I've reproduced it below:

Screen    Optimal Distance

Size       1080p     4k

25"      0.98 m    0.46 m

30"      1.16 m    0.52 m

35"      1.35 m    0.61 m

40"      1.56 m    0.71 m

45"      1.74 m    0.80 m

50"      1.93 m    0.89 m

55"      2.14 m    0.98 m

60"      2.32 m    1.16 m

65"      2.50 m    1.25 m

70"      2.72 m    1.35 m

cheers,

Ian.