Your question was perfectly clear and I answered it 22cm or close to 9 inches is the distance that both lines are equally black. When I zoom out the vertical lines start getting thinner and grey.
When you zoom out do the horizontal lines get thicker and darker? When you zoom in from 22 cm do the horizontal lines get thinner and grey and the vertical lines thicker and darker?
At about 12cm the horizontal lines start to lose focus and get thinner and grey while the vertical is in complete focus. Zooming out from 22cm doesn't make the horizontal lines any thicker or darker.