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Profiling and Gamut Ranges

The profiling procedure helps determine the color gamut of the scanner and to see how far the colors deflect from what they should be. So, I create a profile that can be later used for ensuring a natural color representation by specifying the profile in the driver’s settings. Moreover, I have the digital values of the color tones of the IT8 target which can be used to create the following diagram of the gamut of the Epson Perfection 4490 scanner:

The triangle-outlined gamut is a projection on the plane and shows the scanner’s palette in the visible light spectrum. Knowing the coordinates of the vertexes of the triangles, it is possible to calculate their areas for comparison.

The next diagram is constructed by calculating the difference between the colors of the color target and of its scan. Note that Color Difference values above 5.0 are discernable by most people, i.e. evident for the “average” human eye. 

As you can see, the Perfection 4490 is noticeably worse than the top model of the series when scanning reflective originals. Color discrepancies occur in the darkest areas of the color target. I should note, however, that the manufacturer uses a special lamp in the Perfection 4990 with an intensified blue constituent of the spectrum. The Perfection 4490 lacks this feature and this explains the results.

And the last part of today’s tests is probably the most important of all. It deals with scanning quality.

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