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Volume: 28 | Article ID: art00013
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RED color spaces demystified reverse engineering of RED color by spectral analysis of Macbeth color charts and RED Scarlet-X Camera recordings
  DOI :  10.2352/ISSN.2470-1173.2016.7.MOBMU-286  Published OnlineFebruary 2016
Abstract

Modern digital film cameras are using mostly CMOS- Mosaic-sensors with a Bayer pattern, resulting in a four channel representation of the light from the scene. That four channel may be merged to one channel or kept separately for further processing. This data is known as sensor raw and has at this stage no additional processing applied with the exception of interpolating missing pixels. These signals cannot be displayed properly because the display would need primaries with negative values which is physically not possible. So the data has to be debayered – the two green, one red and one blue color channel are filtered and combined, and then converted, usually by a 3x3 matrix to a certain color space – the Camera RGB color space, which is proprietary by the camera manufacturer. From this stage other 3x3 matrix conversions to different color spaces are possible. There are specified ones like sRGB, ITU BT.709 or Adobe RGB, but also proprietary color spaces by the camera manufacturer, to establish a certain look and feel. This is done by converting the RAW Sensor or the RGB Camera data to their own proprietary color spaces, using a 3x3 matrix. In the case of RED cameras, the color spaces in question are REDspace, REDcolor, REDcolor2, REDcolor3, and REDcolor4. The underlying 3x3 matrixes are not documented and only some verbal description is available. The goal of this paper is to measure the color spectrum of a common Macbeth color chart with a spectral camera under a certain lighting condition. Under the same lighting condition, the Macbeth color chart is recorded by a RED Scarlet-X camera. The data from the spectral is then converted to the CIE xyY-color space and the positions of the 24 Macbeth patches are plotted in the CIE xy- chromaticity diagram. The RED raw footage is also converted to the appropriate RED color spaces linear (i. e. without gamma functions applied) and the positions of the Macbeth color patches are converted to the CIE chromaticity diagram as well. By comparing the different positions of these patches one can tell how the color conversion works and how the certain RED color spaces are related to each other and to the result from the spectral measurement.

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  Cite this article 

Eberhard Hasche, Patrick Ingwer, Reiner Creutzburg, Thomas Schrader, Frederick Laube, Timo Sigwarth, "RED color spaces demystified reverse engineering of RED color by spectral analysis of Macbeth color charts and RED Scarlet-X Camera recordingsin Proc. IS&T Int’l. Symp. on Electronic Imaging: Mobile Devices and Multimedia: Enabling Technologies, Algorithms, and Applications,  2016,  https://doi.org/10.2352/ISSN.2470-1173.2016.7.MOBMU-286

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