Question:
The human eye has an approximate angular resolution of φ = 5.8 × 10–4 rad and a typical photo printer prints a minimum of 300 dpi (dots per inch, 1 inch = 2.54
cm). At what minimal distance z should a printed page be held so that one does not see the individual dots.
Solution:
Angular separation, φ = 5.8 × 10–4 rad
The average distance between the two dots = 2.54/300 = 0.85 × 10-2 cm
At distance z cm, the angle subtended = 0.85 × 10-2/z
Resolution angle for human = 0.85 × 10-2/z
Maximum distance between 2 dots = z = 14.5 cm
The above distance is less than the distinct vision, which normal person cannot see.