I stumbled across this topic for this week’s blog by accident while browsing the web. Although this is not related to supply chain technology, I thought it was sufficiently high-tech to merit some general interest. I hope you find the topic as interesting as I do.

To begin, let’s review how color photographs are produced by digital cameras. The sensor in a camera cannot directly see color – it can only see intensity of light. When you see a camera advertised as “10 megapixels,” it means there are 10 million light-sensitive photoreceptors on the camera’s “digital film” chip. These photoreceptors record the intensity of the light that falls on them, from zero (black) to high intensity (white). Left to themselves, they produce a black and white image.

But for color, light needs to be broken into primary wavelengths of red, green, and blue (RGB). Combining these three colors in varying intensities creates the full spectrum of color. This is how a digital camera produces a color image. Each photoreceptor in the camera is fitted with an individual red, green, or blue lens that filters the light that falls onto the sensor. 

With this RGB filter in place, the digital information records varying intensities of red, green, and blue light at discrete points in the image. Powerful image-processing algorithms scan this information into the onboard microprocessor’s memory.

 

On high-end digital cameras, you can change the behavior of the algorithm by setting values for hue, intensity, white balance, contrast, and other variables. The electronics in the camera then go to work to produce a color image from individual pixels of red, green, and blue light intensity information. 

The scientific fact that color can be generated from red, green, and blue light has been known since well before the invention of photography. Since the late 1800s, there have been laboratory experiments in color photography. Technological factors, however, limited the practical majority of photographic images to black and white up until the late 1930s (and it was not until the 1960s that color came to the mass market, as immortalized by the Simon and Garfunkel song “Kodachrome”). 

Here’s the really interesting part: On my web search, I found that there was one early photographer who developed an elegant approach to color photography. He was a Russian named Sergei Mikhailovich Prokudin-Gorskii. He was familiar with theories that one could create a color image by taking successive black and white images through red, green, and blue filters.

 

The three black and white images would show the same scene, but differ in shading and light intensity according to the filter used. 

Ahead of his time, in the early 1900s, Prokudin-Gorskii built a custom camera to accomplish this task.

He also built a projector that would allow him to show audiences color images projected on a screen. He was successful enough that the Tsar commissioned him to go on a photographic expedition to document the Russian Empire. These trips occurred from 1905–1915. 

The expedition produced thousands of glass plate negatives. These could be printed and displayed as conventional black and white images for publication and exhibition. However, the projection apparatus needed for producing the color images limited the practical extent to which the images could be published in full color.

Then came the Russian Revolution, which was a disaster for Prokudin-Gorskii and all other friends of the Tsar. He fled Russia. His collection of glass plate negatives ultimately wound up in the archives of the US Library of Congress, where they sat in obscurity.

With the advent of digital photography, a curator in the Library of Congress realized that the Prokudin-Gorskii photographs could be displayed in a manner never before possible. In 2004, the Library of Congress commissioned a restoration project. Each set of negatives was scanned into a computer, aligned, and color-adjusted in exactly the same manner as an image is produced within a digital camera.

 

The results were glorious. They are viewable at the Library of Congress website at the following link: http://www.loc.gov/exhibits/empire/

These photographs represent a treasure trove of historical documentary images. They also represent the perfect combination of scholarship, luck, and high-tech restoration.

-- Paul

 

Photo Credit: Library of Congress