Editing Image scanner (section)

==== Analog scanners{{Anchor|Analog era}} ====
Before the advent of [[digital image processing]] in the middle of the 20th century, the term ''scanner'' originally referred to analog equipment used within [[Offset printing|offset printing press]]es. These analog scanners varied in design depending on their purpose: some scanned images stored as [[color transparency film]] onto [[color separation]] plates that could be used to print the original image en masse; while others were used to convert simple [[CMY color model|cyan, magenta, and yellow]] (CMY) plates into [[CMYK color model|cyan, magenta, yellow, and black]] (CMYK) in order to produce prints with darker, richer colors—a process known then in the trade as color correction (unrelated to the modern, [[Color correction|cinematographic sense]]). Converting from CMY to CMYK used to be a highly manual affair involving techniques such as [[Masking (art)|masking]]. Analog scanners automated this process to a large extent.<ref name=principles>{{cite book | last=Yule | first=J. A. C. | date=2000 | edition=Updated Reprint | orig-date=1967 | url=https://archive.org/details/principlesofcolo0000yule | title=Principles of Color Reproduction: Applied to Photomechanical Reproduction, Color Photography, and the Ink, Paper, and Other Related Industries | publisher=GATFPress | isbn=088362222X | via=the Internet Archive}}</ref>{{rp|305}}

Alexander Murray and Richard Morse invented and patented the first analog color scanner at [[Eastman Kodak Company|Eastman Kodak]] in 1937. Their machine was of a [[drum scanner]] design that imaged a color transparency mounted in the drum, with a light source placed underneath the film, and three [[photocell]]s with [[RGB color model|red, green, and blue]] color filters reading each spot on the transparency to translate the image into three electronic signals. In Murray and Morse's initial design, the drum was connected to three [[lathe]]s that etched CMY [[Halftone|halftone dots]] onto three offset cylinders directly. The rights to the patent were sold to Printing Developments Incorporated (P.D.I.) in 1946, who improved on the design by using a [[photomultiplier tube]] to image the points on the negative, which produced an amplified signal that was then fed to a single-purpose computer that processed the RGB signals into color-corrected CMYK values. The processed signals are then sent to four lathes that [[Photo etching|etch]] CMYK halftone dots onto the offset cylinders.<ref name=hunt>{{cite book | last=Hunt | first=R. W. G. | date=2005 | url=https://books.google.com/books?id=Cd_FVeuO10gC | title=The Reproduction of Colour | publisher=Wiley | pages=519–523 | isbn=9780470024263 | via=Google Books}}</ref><ref name=molla>{{cite book | last=Molla | first=Rafiqul K. | date=1988 | url=https://archive.org/details/electroniccolors0000moll/page/34/ | title=Electronic Color Separation | publisher=R.&nbsp;K. Printing and Publishing | page=34 | isbn=0962045306 | via=the Internet Archive}}</ref>

In 1948, Arthur Hardy of the Interchemical Corporation and F.&nbsp;L. Wurzburg of the [[Massachusetts Institute of Technology]] invented the first analog, color flatbed image scanner,<ref>{{cite book | last=Hand | first=Di | author2=Steve Middleditch | date=2014 | url=https://books.google.com/books?id=JXwABAAAQBAJ | title=Design for Media: A Handbook for Students and Professionals in Journalism, PR, and Advertising | publisher=Taylor & Francis | page=24 | isbn=9781317864011 | edition=ebook | via=Google Books}}</ref> intended for producing color-corrected [[Lithography|lithographic]] plates from a color negative. In this system, three color-separated plates (of CMY values) are prepared from a color negative via [[dot etching]] and placed in the scanner bed. Above each plate are rigidly fixed, equidistant [[light beam]] projectors that focus a beam of light onto one corner of the plate. The entire bed with all three plates moves horizontally, back and forth, to reach the opposite corners of the plate; with each horiztonal oscillation of the bed, the bed moves down one step to cover the entire vertical area of the plate. While this is happening, the beam of light focused on a given spot on the plate gets reflected and bounced off to a photocell adjacent to the projector. Each photocell connects to an [[Analog image processing|analog image processor]], which evaluates the [[reflectance]] of the combined CMY values using [[Neugebauer equations]] and outputs a signal to a light projector hovering over a fourth, unexposed lithographic plate. This plate receives a color-corrected, [[continuous tone|continuous-tone]] dot-etch of either the cyan, magenta, or yellow values. The fourth plate is replaced with another unexposed plate, and the process repeats until three color-corrected plates, of cyan, magenta and yellow, are produced. In the 1950s, the [[RCA|Radio Corporation of America]] (RCA) took Hardy and Wurzburg's patent and replaced the projector-and-photocell arrangement with a [[video camera tube]] focusing on one spot of the plate.<ref name=hunt /><ref name=molla />