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Jan Hubička edited this page Jul 13, 2024 · 16 revisions

Color models

Result of some rendering modes (such as interpolated) is an RGB image in the color space of the color process used to take the photogrpah. In order to display it correctly, it is necessary to convert it to modern color space (such as sRGB, ProphotoRGB or XYZ). Color models define how colors are converted. The following are available

none

Perform no color transformations. Useful for debugging

red, green, blue

Shown red, green or blue separation

Wall max separation

Use colors that are best separating human vision according to book: Wall EJ. Practical color photography. American Photographic Publishing Company; 1922.

"We may, therefore, say that there are three fundamental or primary colors in the spectrum, by the admixture of which we can form all intermediate colors and white. The positions of these fundamental colors are shown by the heavy vertical lines R. G. B,, in Fig. 3, and the curves show how the intermediate colors are formed. It will be seen from the diagram that the fundamental red is at about 6700, and this excites but the one sensation; but the green at 5180 not only excites the green-sensitive nerve fibril but also the red and the while the blue blue,at 4600 excites the green and red also, though but slightly."

This is interpreted as xy values

  • red: 0.7319933,0.2680067 (670nm)
  • green: 0.059325533,0.829425776 (518nm)
  • blue: 0.143960396, 0.02970297 (460nm)

paget

RGB values which looked good for early set of scans of paget plates available. This setting will be replaced by better one once paged color dyes are understood

This is interpreted as xy values

  • red: 0.674, 0.325
  • green: 0.059325533,0.829425776
  • blue: 0.143960396, 0.02970297

Miethe_Goerz_reconstructed_by_Wagner

Colors used in Goertz projector (designed by Miethe) as reconstructed in Wagner, J. (2006) Die additive Dreifarbenfotografie nach Adolf Miethe. Master thesis. Technische Universität München.

This is interpreted as xy values

  • red: 0.674, 0.325
  • green: 0.182, 0.747
  • blue: 0.151, 0.041

Miethe_Goerz_mesured_by_Wagner

Colors of aged filters used in Goertz projector (designed by Miethe) as measured in Wagner, J. (2006) Die additive Dreifarbenfotografie nach Adolf Miethe. Master thesis. Technische Universität München.

This is interpreted as xy values

  • red: 0.620, 0.315
  • green: 0.620, 0.315
  • blue: 0.182, 0.135

Wratten_25_58_47_xyz

Those are colors of Wratten filters 25, 58 and 47 which were used as standard filters for three-color photography. Based on MacAdam, D. L. Colorimetric specifications of Wratten light filters. Journal of the Optical Society of America 35, 10 (1945), 670–675.

These are XYZ values

  • red: 0.3038, 0.1425, 0.0001
  • green: 0.0891, 0.2451, 0.0219
  • blue: 0.0862, 0.0240, 0.4730

Wratten_25_58_47_spectra

Colors based on spectrum of Wratten filters as published by Kodak "Wratten light color filters, 1945 edition.". Those are tables XYZ values above are based on. Advantage of having full spectrum is that colors can be viewed with different backlights.


Digitized data based on published table

Data can be exported using colorscreen lab save-dyes wratten-red.dat wratten-blue.dat wratten-green.dat wratten_25_58_47_kodak_1945.

dufaycolor_reseau_by_dufaycolor_manual

Spectra based on charts in the Dufaycolor manual. Those are clearly not realistic, but represents the intended sensitivity of the film.


Published chart

Digitized data

dufaycolor_reseau_by_color_cinematography_xyY

xyY specification of Dufaycolor reseau filter in Cornwell-Clyne, Adrian (1951) Colour Cinematography. Third. Champman & Hall. Available at:https://archive.org/details/dli.ministry.11295.

Table is (in xyY):

  • red: 0.633, 0.365, 0.177, Dominating wavelength 601.7
  • green: 0.233, 0.647, 0.43, Dominating wavelength 549.6
  • blue: 0.140, 0.089, 0.037, Dominating wavelength 466.0

We believe the table is faulty since the dominating values does not correspond to the xyY values specified. Also it makes the overall reseau filter to look green.

dufaycolor_reseau_by_color_cinematography_xyY

Our attempt to correct the table (in xyY):

  • red: 0.633, 0.365, 0.177
  • green: 0.233, 0.647, 0.43
  • blue: 0.164, 0.089, 0.087

dufaycolor_reseau_by_color_cinematography_wavelength

Colors based on dominating wavelength data in the table discussed above

dufaycolor_reseau_by_color_cinematography_spectra


Published chart

Digitized data

Spectrum published in Cornwell-Clyne, Adrian (1951) Colour Cinematography. Third. Champman & Hall. Available at:https://archive.org/details/dli.ministry.11295.

dufaycolor_reseau_by_color_cinematography_spectra_correction

"Camera profile" based on the previous spectral measurement and estimate of the spectral resonse of Dufaycolor emulsion. This compensates for some weak points of the process (such as desatured yellows) and can make correction of color cast based by different spectra of the light when photograph was taken.

dufaycolor_reseau_by_harrison_horner_spectra


Published chart (better scan would be greatly appreciated)

Digitized data

Spectrum published in Harrison, Horner: Principles of Dufaycolor printing, The photographic journal, 1939

dufaycolor_reseau_by_harrison_horner_spectra_correction

"Camera profile" based on spectrum above.

dufaycolor_reseau_by_collins_giles_spectra


Published chart (better scan would be greatly appreciated)

Digitized data

Spectrum published in Collin, Giles: Color photography, Journal of society of dyers and colorist, 1952 ### dufaycolor_reseau_by_collins_giles_spectra_correction "Camera profile" based on spectrum above.

dufaycolor_photography_its_materials_and_processes


Published chart (better scan would be greatly appreciated)

Digitized data

Spectrum published in C. B. Neblette: texts Photography, its materials and processes 1952

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