halftone process

As part of my Design Context publication is most likely going to be an exploration about how graphic processes have evolved, I wanted to look at halftone. This has always been a puzzle to me and I have been fascinated by them since I was young. I remember newspapers were far cruder in the way they were printed and the halftones used to replicate photographs were very noticeable, but I never understood why, and how they were used.

Its actually a fairly old process: this, as far as I can tell, is the first printed halftone photo, from 1873!

To really explain the process, I found this link very useful:
http://www.ted.photographer.org.uk/photoscience_halftones.htm