It said: No closer than 40 cm (15.7 inches) and no farther than 70 cm (27.5 inches). Optimal 50 cm (19.6 inches).
And that is for a 26" monitor. So I imagine it would be little bit different for a 22" monitor. It looks like I am in the ballpark.
Arms length away or slighter further and eyes aligned with the top or slightly below the top for larger displays.
I've tried several scenarios but what comes back to be more natural is about my arm's length, on a 21" 4:3.
Now if you compare a 30 inch screen which has similar pixel density, would you sit just as close as you did with the 20 inch or would you sit back. Keeping in mind that the text is similar in size when both screens are running in their native resolution.
thats the whole problem I see with 30 inchers running 2560x1600. there's just no sweet spot for viewing them. if you're sitting close enough to distinguish individual pixels, then you're eyes will have to work harder to see the extremities of the screen. Too far back, and you won't be able to distinguish the pixels.
for multi-tasking 2560x1600 makes sense, but for concentrating on one image, I think 2560x1600 is just illogical, our eyes cannot notice all those pixels at the same time. thats not to say a 30 incher sporting 2560x1600 isn't impressive, it's just not fully realized by our eyes.