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Color-Screen

Color-Screen is a collection of tools for working with scans of additive screen processes of early color photography.

Flowers, Paget lantern slide 8x8cm, ca 1921 (left) and digital color reconstruction (right)

What is an additive color screen process?

Additive color screen processes used panchromatic negative which was exposed through a color screen filter pretty much same was as today CCD and CMOS chips use Bayer filter. The negative was then copied to (black and white) transparency which yield to color picture when viewed through the viewing screen filter.

What we aim for?

Our tool can:

• Turn scans of negatives taken using additive color screen filters to color photographs with a high degree of color accuracy (relative to colors which was achievable by the analog way).
• Recover original colors of transparencies which faded or got misregistered. These transparencies sandwich black and white slide with a color screen. If digitized in infrared spectra one can obtain a scan of the slide (screens are transparent) and then re-add the screen digitally.
• Make the photographs easy to view on digital screen and prints. Scans of additive color screen processes are hard dispay or print because the color screen patterns become more apparent than in the original and colors gets shifted. It is a common practice to digitize them in low resolution or somewhat out of focus to reduce unwanted artifacts or apply various noise reduction tools. We implement special demosaicing algorithms which understand the specific color screen used and produce smoother digital file without losing fine details of the image.

Software packages

• ColorScreenGUI: Java based GUI
  • Development snapshot built for Windows
  • Development snapshot built for MacOS (untested)
• colorscreen: Library, command line utility and a legacy GTK2 based GUI
  • Color-Screen version 1.0, release candidate 2 (source code)
  • Color-Screen version 1.0, release candidate 2 (MacOS binary, untested)
  • Color-Screen version 1.0, release candidate 2 (Windows binary)

Table of contents

• Rendering Algorithms: Description of Color-Screen's rendering pipeline and main parameters
• Supported Processes: List of supported processes
• Collections: Known collections of additive color screen processes around the world
• Available scans of color screen processes: List of scans available online Color-Screen can be applied to.
• Digitization: Guidelines for digitizing additive color processes
• Color-Screen documentation
  • colorscreen: Using the command line utility
• Publications