Irradiance‐independent camera color calibration. Issue 6 (30th October 2013)

• Record Type: Journal Article
• Authors: Funt, Brian; Bastani, Pouya
• Is Part Of: Color research & application. Volume 39:Issue 6(2014:Dec.)
• Page Start: 540
• Page End: 548
• Publication Date: 2013-10-30
• Subjects: Color -- Periodicals; 535
• DOI: 10.1002/col.21849
• Languages: English
• ISSNs: 0361-2317

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>For a digital color camera to represent the colors in the environment accurately, it is necessary to calibrate the camera <italic>RGB</italic> outputs in terms of a colorimetric space such as the CIEXYZ or sRGB. Assuming that the camera response is a linear function of scene luminance, the main step in the calibration is to determine a transformation matrix <bold><italic>M</italic></bold> mapping data from linear camera <italic>RGB</italic> to <italic>XYZ</italic>. Determining <bold><italic>M</italic></bold> is usually done by photographing a calibrated target, often a color checker, and then performing a least‐squares regression on the difference between the camera's <italic>RGB</italic> digital counts from each color checker patch and their corresponding true <italic>XYZ</italic> values. To measure accurately the <italic>XYZ</italic> coordinates for each patch, either a completely uniform lighting field is required, which can be hard to accomplish, or a measurement of the illuminant irradiance at each patch is needed. In this article, two computational methods are presented for camera color calibration that require only that the relative spectral power distribution of the illumination be constant across the color checker, while its irradiance may vary, and yet resolve for a color correction matrix that remains unaffected by any irradiance variation that may be present. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 540–548, 2014</p> </abstract>