by Mike McNamee Published 01/12/2009
The RAW file could not be opened in ACR; a couple of seconds after caching the files from the camera, the thumbnails turned bright green, as did the processed file. This apparently is something others have found trying to use ACR and DP2 RAW files. For the record we were using ACR Version 5.5, the most up-to-date and the DP2 is not listed by Adobe as a supported camera.
To get around the problem we extracted the Sigma RAW file using Adobe DNG converter and returned an identical error of 5.4 ΔE 2000.
We then made the same corrections of brightness and white balance and returned an error of 4.87 ΔE2000.
Overall the RAW file was a better rendition than the JPEG, mirroring the reported findings from other people.
Use of the Rags Gardner ACR calibrator reduced the average error yet further, achieving a creditable 3.02 ΔE2000. The Lab plot and the TIFF file with the target overlay colours reveal all. The length of the arrows show the size of the error - longer is worse. When the arrow extends directly away from the origin of the graph the error is in saturation, if the arrow is rotated away from that axis the error is also in hue. Hence the error in yellow is in both hue and saturation, and is small. The error in the red is large and is mainly due to the result being over saturated. These effects are visually apparent in the TIFF image. The red carried the highest error at 16.3 ΔE Lab points, the purple was not far behind at 14.2 points. The best rendered colours were in the greencyan-blue quadrants.
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