Scarica gli atti - Gruppo del Colore

any previous linearization step. Lastly, we evaluated whether the lens employed
generates any geometrical distortion by acquiring a home-made calibration target;
our trials showed that no distortions are generated.
Fig. 2 – A shot of our acquisition system. It can be mounted on a tripod but also hanged
from above using a simple frame like this one
At the beginning of an acquisition session, if we do not already have an empirical
characterization model for that light setup, we build one using the Macbeth
ColorChecker DC as our training set. We then proceed to the acquisition of our
intended target, as well as of a reference sheet of paper to be used in discounting
the geometry of illumination. Following CIE recommendations, we estimate
reflectance at intervals of 10 nanometers in the range 400 nm to 700nm; we
therefore employ thirty-one different configurations of our tunable filter so as to
avoid ending up with an underdetermined system in Equation 9. These
configurations are chosen so that the peak of the corresponding filter transmittance
also varies between 400 nm and 700 nm with steps of 10 nm.
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