Due to the difficulty in reproducing prints of sufficient quality from the negatives, only some hundred were used for exhibits, books and scholarly articles after the Library of Congress acquired them.[4] The best-known is perhaps the 1980 coffee table book Photographs for the Tsar: The Pioneering Color Photography of Sergei Mikhailovich Prokudin-Gorskii Commissioned by Tsar Nicholas II,[19] where the photos were combined from black-and-white prints of the negatives.[20]
It was only with the advent of digital image processing that multiple images could be satisfactorily combined into one.[21] The Library of Congress undertook a project in 2000 to make digital scans of all the photographic material received from Prokudin-Gorsky's heirs and contracted with the photographer Walter Frankhauser to combine the monochrome negatives into color images.[22] He created 122 color renderings using a method he called digichromatography and commented that each image took him around six to seven hours to align, clean and color-correct.[23] In 2001, the Library of Congress produced an exhibition from these, The Empire That Was Russia: The Prokudin-Gorskii Photographic Record Recreated.[24] The photographs have since been the subject of many other exhibitions in the area where Prokudin-Gorsky took his photos.[25][26][27][28][29][30]
http://en.wikipedia.org/wiki/Sergey_Prokudin-Gorsky