Methods of selecting a small reflectance set as a transfer standard for correcting spectrophotometers

Reflective color reduction using genetic algorithm optimization

“…There are many ways to select the training subset. For example, we can randomly pick 12 colors from the 1950 NCS full set, or we can use culling algorithm as described by Ingleson and Brill . In this article, we will discuss a GA, and compare its performance with the random pick and culling algorithm.…”

“…The “inner loop” subroutine (Figure ) is a culling algorithm, and is in fact the same algorithm used in Ref. —but on a much‐reduced subset of colors. The metric used to evaluate the performance is the average Δ E ab * of the full set of 1950 NCS colors, meaning that after the spectrum transformation matrix was obtained using the selected subset of colors, all the 1950 NCS colors were converted from 10‐channel sensor readings to 32‐wavelength spectra (from 400 to 710 nm with 10‐nm intervals), and the converted spectra were compared to the original ones to get the difference Δ E ab * of each color; then the average Δ E ab * of all the 1950 colors was calculated and used to evaluate the matrix transformation performance.…”

“…For example, we can randomly pick 12 colors from the 1950 NCS full set, or we can use culling algorithm as described by Ingleson and Brill. 8 In this article, we will discuss a GA, and compare its performance with the random pick and culling algorithm. It should be understood that there are other ways of optimization for the selection of a training subset, but they are out of the focus of this article and will not be discussed here.…”

“…In reflective color samples, there is also a need to find a subset of colors that represents a much larger color set. For example, in Ingleson and Brill's 2006 article, a culling algorithm was used to choose the best subset of a few reflectances from a large set of reflectances to act as a transfer standard. In such cases, the subset of colors needs to discern the spectral shift between two instruments effectively, and thus the color selection and optimization need to be done in the space of reflectances.…”