In a previous post, I described how I had created a Matlab program to analyze sets of reflectance spectra, generate basis functions, and then use those basis functions to produce metamer sets, all with an arbitrary fixed color. For review, here is the methodology I used: Using principal component analysis, find a set of basis… [Read More]
Archives for April 2022
Nikon Z9 goes to an event
After more than two years of semi-isolation, I stepped out last weekend. The occasion was a middle-school play. Much of my family, a couple of hundred other mostly-maskless people of unknown vaccination status, and I crammed ourselves into a room to watch the youngsters perform. I brought the Z9 and one lens: the 70-200/2.8 S…. [Read More]
Natural colors — reflectance spectra metamers
In preparation for some work that I’ll be doing about observer metameric errors in digital cameras, I’ve built a program that, given a target color and a set of sample reflectance spectra, will: Using principal component analysis, find a set of basis functions for the sample set Assuming the set is lit with a particular… [Read More]
Dimensionality of patch sets and natural spectra
A DPR PS&T member kindly supplied me with a collection of reflectance spectra about 220 natural objects. I added that set to my other patch sets, and performed a principal component analysis (PCA) on each set. One thing I did differently this time is I restricted the wavelengths under consideration to the set between 400… [Read More]
Training on the ColorCheckers, testing on natural spectra
Using the natural reflectance spectra that a DPR PS&T member supplied me, and illuminating all the samples with D50 light, I looked at the errors with an optimized compromise matrix generated by training on the CC24, the CC SG, the CC Passport, and the natural spectra themselves. As expected, training on the natural spectra was… [Read More]