It is well understood that the color values from a digital camera are functions of the camera's spectral sensitivities, the reflectances of the objects in the scene as well as illumination and any filter that is placed between the object and the sensor. It is vital to select the correct illumination to optimize a color reproduction pipeline. In practice, the choice of the illumination is limited to the spectra of available light sources.<br/> In this paper, we optimize a camera's colorimetric performance by theoretically mounting a filter to the lens. An ideal spectrum of the filter is obtained using the Luther optimization condition. By using variational calculus we reduce the optimization problem to a system of non linear equations on a Lie group. We solve the system of equations by applying Newton's method on a Lie group with a left invariant Riemannian structure. As expected from the literature, our experiments show quadratic convergence.<br/> A second approach is a redesign of the set-up. This redesign gives us a quadratic optimization problem that is easier to solve. Constraints to this optimization problem gives us control on the transparency of the filter.
The variability of human observers and differences in the cone photoreceptor sensitivities are important to understand and quantify in the context of Color Science research. Differences in human cone sensitivity may cause two observers to see different colors on the same display. Technicolor SA built a prototype instrument that allows classification of an observer with normal color vision into a small number of color vision categories. The instrument is used in color critical applications for displaying colors to human observers. To facilitate Color Science research, an Observer Calibrator is being designed and built. This instrument is modeled on one developed at Technicolor, but with improvements including providing higher luminance levels to the observers, a more robust MATLAB computer interface, two sets of individually controlled LED primaries, and the potential for interchangeable optical front ends to present the color stimuli to observers. The new prototype is lightweight, inexpensive, stable, and easy to calibrate and use. Human observers can view the difference between two displayed colors, or match one existing color by adjusting one LED primary set. The use of the new prototype will create opportunities for further color science research and will provide an improved experiment experience for participating observers.