Continuous-tone graphs are reproduced for publication in newspapers, magazines & books with a printing process called half toning, & the reproduced pictures are called halftones. For a black and white photograph, each intensity area is reproduced as a series of black circles on white background.
The diameter of each circle is proportional to darkness required for that intensity region. Darker regions are printed with large circles , Lighter regions are printed with small circles. Books and magazine are printed on high quality paper using 60 to 80 circles of varying diameter per centimeter. Newspaper use lower quality paper and lower resolution.