a = repmat([1 0],1000,500);
I put the images on my 24 inch LED Cinema Display, and on my 15 inch Macbook Pro. I measured the distance I had to move my eyes away from the display to make the lines disappear. The results were the same for the horizontal and vertical lines (both devices have square pixels so the numbers are the same as wel), so I only put the results for the vertical lines (horizontal resolution) in the table.
I couldn't figure out how to make a table on the forum so the table is over here:
Eye resolution comparison table
You can download the images here and do the test for yourself:
Make sure you put your viewer on "actual size" (in Preview.app this is command-0).
I also put the Matlab script and the spreadsheet (OpenOffice format) in the directory in the second link, so you can play with it.
It turns out that my eyes have a resolution of a little bit more than 0.6 arc minutes, using this test. The last column in the table gives the values for the iPhone 4. I used 304 mm, which is 12 inches, because that is what Steve Jobs said. This is 0.88 arc minutes, so I guess I will be able to see pixels when holding the iPhone4 at a 12" distance.
I tend to use my iPhone at a distance of between 300 and 500 mm, depending on what I'm doing. I guess it's still an awesome display btw.