Question

The human eye has an approximate angular resolution of $\varphi =5.08\times 10^{-4}rad$ and typical photoprinter prints a minimum of $360$ dpi (dots per inch, $1$ inch $=2.54cm$ ). At what minimum distance, $Z$ (in $cm$ ) should a printed page be held so that one does not see the individual dots?

Answer 1

Answer: 13.89

Here, angular resolution of human eye, $\varphi =5.08\times 10^{-4}rad$
The linear distance between two successive dots in a typical photoprinter is
$l=\frac{2.54}{360}cm$
At a distance of $Zcm$, the gap distance $l$ will subtend an angle,
$\varphi =\frac{l}{Z}$
$\therefore Z=\frac{l}{\varphi }$
$=\frac{2.54\times 10^{-2}}{360\times 5.08\times 10^{-4}}$
$=13.89cm$