A common method used to assess color in an image is to photograph a reference reflectance target (i.e., a color chart) that includes a set of color patches with specified characteristics and reference color values. The target is usually photographed at the beginning and at the end of the session, but it can also be included within each image. The intention is to calibrate the colors in the image so that they explicitly represent the original object being photographed.
In Capture One, the accuracy of the colors in the image is assessed by processing and comparing the measured color values using the readouts feature with the reference values for those patches.
Before measurement begins, it is necessary to adopt a color profile representing the capture set-up. Otherwise, change the processing parameters to ensure the processed image of the target is near to the stated reference. In many cases, the reference is specified in the CIE 1976 (L*, a*, b*) color space, often referred to as CIELAB or more simply LAB (or just “Lab”).
For critical comparison, the capture process typically requires an accurate color profile to be adopted, either one created in-situ or a bespoke profile that includes the specific camera and illuminant (i.e., light source) for the set-up. Besides taking into account the color temperature, measurement of the illuminant or light source must also include the geometry of the set-up (usually D50 at 45-degree angle of illumination) and the average human color vision (an observer model, usually the CIE 1931 2-degree Standard Observer). This device profile and the one used during output for further analysis in third-party software typically adopt an RGB color space.
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