|Reproduction of a bison of the cave of Altamira|
It gets a little bit involved to understand the concepts and what is actually going on when we talk about digitizing something. Stay with me and I will walk you through how all this came about.
Since ancient times, humans have tried to capture and preserve their impressions of the physical world. The cave painting depicted above is an example of what could be called an "analog" image. What we mean by an "analog image" is that the method of reproduction of the physical reality is also a physical reality. At the time this image was painted on the wall of the cave, there really was a bison out there in the world running around and eating grass. The technical definition of an analog image would be something like this: relating to or using signals or information represented by a continuously variable physical quantity such as spatial position or voltage. In the case of the cave painting, the "continuously variable physical quantity" is the paint used.
When a genealogist looks at a document or other record of the past and copies out the information contained in the document, he or she is making an "analog" copy of the information using a pen or pencil and a piece of paper. Obviously, the cave painting above is not an exact replica of the original bison. Just as obviously, the pen or pencil copy of the information in a source document is also not an exact replica of the original. But for thousands of years, the only way to make a copy of a document at all was to copy it by hand. Printing was invented to speed up the process and enable the printer to make multiple copies of the same document. But each of those individual copies was still an "analog" of the original. Making any changes to the original analog copy essentially required remaking an original. If a painter painted a painting of a landscape, the only way I could acquire a copy of the painting was if someone copied the original in some format.
In 1725, the limitation on making copies of an original began to change when Johann Heinrich Schulze made fleeting "photographs" of words by using stencils, sunlight, and a bottled solution of chalk and silver nitrate, simply as an interesting way to demonstrate that the mixture inside the bottle darkens where it is exposed to light. See Wikipedia, Timeline of photography technology.
If we fast forward through the history of the development of photography, we see that what was happening was that the inventors and developers of the photographic process were working on a new analog process of reproducing images. As photography developed, it became possible to use a camera to take a negative image (first negative invented in 1835 by Henry Fox Talbot) and then make as many positive image copies as desired of the "original" analog photograph. The media for the analog image was the glass plate or film. See Wikipedia, Timeline of photography technology.
Fast forwarding this whole process, for genealogists, the breakthrough for preserving documents came with the introduction of microfilm copies of the originals. The earliest microphotographs were made by John Benjamin Dancer in 1839, shortly after the introduction of the daguerreotype process. See Wikipedia: Microform.
It is important to remember that all this fancy photographic stuff was still an analog of the physical reality as long as it involved some kind of physical film for capturing the image. What was important about film photography was the ability to make multiple copies rather cheaply and easily. Photography did for images what book printing did for books.
So where do digital images come into all this? At the same time photography began to develop, the idea of manipulating information using mechanical and electronic devices also was beginning to emerge. A detailed history of computers is interesting, but beyond the scope of this post series. It is enough to say that the idea of a general-purpose computing device is usually attributed to Charles Babbage, who conceptualized the first mechanical computer beginning in 1833. See Wikipedia: Computer. It was necessary for a lot of other types of technology to develop before the first images could be transmitted electronically in 1920. Quoting from the Wikipedia article on Digital Imaging:
The first digital image was produced in 1920, by the Bartlane cable picture transmission system. British inventors, Harry G. Bartholomew and Maynard D. McFarlane, developed this method. The process consisted of “a series of negatives on zinc plates that were exposed for varying lengths of time, thus producing varying densities,”. The Bartlane cable picture transmission system generated at both its transmitter and its receiver end a punched data card or tape that was recreated as an image.
What happened here is that the "analog" representation of the physical reality had been transformed into a coded representation of the original in the form of electrical impulses. You could argue that this was still an "analog" image and that the medium of transmission had merely changed, but this development was significant to warrant a new category of "digital images." The word "digital" in this context focuses on the fact that the physical reality of the original is represented by a stream of electronic impulses. In the case of the original image transmission back in 1920, the punched data card or tape, was not recognizable as an image until it was processed by the receiver.
The first digital photograph is attributed to Russell Kirsch in 1957. Here is a copy:
|Pioneering digitally scanned image of Russell Kirsch's son Walden, 1957|
The first digital camera is believed to be developed by Kodak in 1975. See "The World’s First Digital Camera by Kodak and Steve Sasson." Although the circuits and the devices have become smaller and smaller, the idea that an image can be made by discrete electronic sensors is at the heart of a digitalization. You could argue that the first movable type book was merely a small step from the original handwritten books, but this small step changed the world. Likewise, the first digital images began the same fundamental revolution in the way information was processed and transmitted.
So, digitization is the process of taking a physical object (book, document, etc.) and using an electronic sensor, transforming the light rays from the object into a series of electronic impulses that can be transmitted, stored, manipulated and altered in an almost infinite number of ways.