Alternative printing processes

I the course of my carreer as a photographer I experimented with some old methods of printing a picture. I made gum bichromate prints and helioengravings. On this page I will com e to explain how these methods work and wil give you links to people that work with it

 

Alot of information can be found on a website of a colleague photographer of mine http://www.alternativephotography.com/wp/processes

Gum bichromate printing

A nice description can be found in the following PDF file An Introduction
to the Gum Bichromate Process

Making Color Images from Prokudin-Gorskii’s Negatives

An Explanation of the Color Rendering Process, “Digichromatography”

	There is no known replica or illustration of the camera that Prokudin-Gorskii used. It was a view camera of his own design, perhaps similar to a model [left] designed about 1906 by Dr. Adolf Miethe, whom Prokudin-Gorskii had met previously in Germany. Miethe, Adolf, 1862-1927. Camera and Casette, ca. 1906. Illustration from Fotograf-Liubitel 17, no. 12 (December 1906): 5. General Collections, Library of Congress
We know that Prokudin-Gorskii intended his photographic images to be viewed in color because he developed an ingenious photographic technique in order for these images to be captured in black and white on glass plate negatives, using red, green and blue filters. He then presented these images in color in slide lectures using a light-projection system [right] involving the same three filters. Lantern Projector Thomas Cradock Hepworth. Book of the Lantern. New York: Edward L. Wilson, 1889.
	A single, narrow glass plate about 3 inches wide by 9 inches long was placed vertically into the camera by Prokudin-Gorskii . He then photographed the same scene three times in a fairly rapid sequence using a red filter, a green filter and a blue filter.
When viewed through Prokudin-Gorskii’s camera, the scene being photographed would have appeared upside down and reversed from its actual orientation. Left: Photograph of Glass Plate Right: Inverted View Through Camera Lens
	For the digital process, the original tri-part glass negative is scanned with an overhead digital camera in grayscale mode. Image-editing software converts the scan of the entire plate from negative to positive form. The scan is inverted to represent the original physical orientation.
The entire plate is then reduced to 8-bit grayscale mode. Under magnification, the quality of each image on the plate is reviewed for contrast, degree of color separation, extent of damage to the emulsion, and any other details that might affect the final color composite.
	The scan of the entire plate is aligned and the outside edges are cropped.
An electronic file is created for each image from the cropped tri-part plate forming three separate “layers” from which the final color composite will be generated. The layers are labeled by color.
	While still in grayscale mode, the red(R), blue(B), and green(G) layers are aligned forming the “RGB” color composite. This registration process is the most difficult step.
The RGB (Red, Green, Blue) color composite is cropped to eliminate all but the photographic area shared in common by all three layers.
	The cropped color composite is adjusted overall to create the proper contrast, appropriate highlight and shadow detail, and optimal color balance.
Final adjustments may be applied to specific, localized areas of the composite color image to minimize defects associated with over or underexposure, development, or aging of the emulsion of Prokudin-Gorskii’s original glass plate.
	The completed color composite is retouched to minimize defects associated with age and incidental damage.