Visualizing images

Aug 27th, 2010 | Posted by Stone
The Emir of Bukhara

The Emir of Bukhara, reconstructed from the Prokudin-Gorskii 3-color photographic plates, around 1910

The photographs of Sergei Mikhailovich Prokudin-Gorskii (1863-1944) offer a vivid portrait of a lost world–the Russian Empire on the eve of World War I and the coming revolution. Taken between 1909 and 1912, the photographer exposed three glass plates in quick succession, each through a different color filter (red, green and blue). A full color image was recreated by projecting colored light through the plates, using the corresponding filters. The US Library of Congress has recently released a set of digital color images created from these archives that are stunning, with brilliant colors and fine detail. The archive is online, and includes a description of the process they used to recreate the images. This involves first scanning the plates to create three grayscale images, carefully aligning them, then assigning each separation to the corresponding color channel of an RGB image. As part of the process, they repaired flaws in the separations, then adjusted the resulting image to create “the proper contrast, appropriate highlight and shadow detail, and optimal color balance”

While very much admiring their work, my color-geek self immediately wonders how much these digital images really look like the ones the photographer showed his original audiences? The popular press and many internet viewers have marveled at their brilliance. But how much of this was visible in 1910?

Note the rainbow colors in the water, caused by the surface changing during the photographic process. Three-color lantern projector, Thomas Cradock Hepworth, 1889

Looking at one of these images on a digital display is equivalent to projecting with red, green and blue lights the same colors as the display pixels. This is how an LCD display works–you look at the light passing through red, green and blue colored filters. But, the filters used by Prokudin-Gorskii¬† are not the same as those used modern displays.

In an LCD display, the filter colors can be made very saturated and dark because we are looking directly at the light they produce. CRT and plasmas displays use phosphors, producing even more saturated colors, especially blue. Using a projector, the light passes through the filters and is reflected off of a screen or other surface. The result is invariably less saturated due to scattering, and also because a brighter light is needed, which means using less saturated color filters. While wonderful for their time, the audiences of the early 1900′s surely saw images that were much less vivid and colorful.

Rather than historical recreations, these images are marvelous visualizations of the information captured by Prokudin-Gorskii on his glass plates. I suspect he would feel they improve on the visualizations (that is, the projected images) he was able to create.  Appreciate them for what they are, but do not take their colors too seriously as a historical record.

  1. World Wide News Flash
    Aug 27th, 2010 at 17:13
    #1
  2. John Robinson
    Aug 29th, 2010 at 13:56
    Reply | Quote | #2

    Early color photography is inherently not true to color (I have actually made a Photoshop action to correct for the red saturation inherent in Kodachrome). Moreover, most photographs, even modern ones, can benefit from some color balancing. That said, though, usually a mathematical curve adjustment will result in pretty close to true color (assuming only minor deterioration), and I have found that P-G’s method is much closer to the mark than, say, Autochrome, even after all these years. Black and white glass plates preserve their integrity much longer than color prints, due to the chemicals and media involved.

    It’s tempting to say to oneself, for example, “the sky couldn’t possibly be that blue.” Of course it could, this was rural Russia before industrialization and pollution. I suspect that P-G’s aim was to create as realistic an image as he possibly could, and overall I think he did admirably.

  3. Stone
    Sep 3rd, 2010 at 14:31
    Reply | Quote | #3

    The glass plates are an outstanding recording medium, and certainly more stable than color films. And, the results are admirable, no question.

    My point is that we have no way of knowing accurately what colors he a) recorded and b) reconstructed because it depends on precisely the red, green and blue filters he used. The reconstructions by the Library of Congress are one visualization of this information. The projected images P-G created are another. No image will be exactly what he saw. We should admire his work, but there is no way for it to tell us what color the sky really was.

    My comments apply to all photography. When you use a camera to capture a scene, you encode the light and color at each point in a way that depends on the film (or digital sensor) and the exposure. You then create an image based on that encoding, either in the darkroom or with a program like Photoshop. Good photographers make adjustments in both the capture and the reconstruction, applying their skill to get what they consider the best result possible.

  4. John Robinson
    Sep 22nd, 2010 at 20:46
    Reply | Quote | #4
  5. John Robinson
    Sep 22nd, 2010 at 20:50
    Reply | Quote | #5

    @John Robinson
    (would fix my obvious typos but I don’t have an account)