# Deriving the cone fundamentals: a subspace intersection method

## TL;DR

This paper introduces a new computational method to estimate human cone fundamentals using only data from dichromatic observers in color matching experiments.

## Contribution

A novel computational method to estimate cone fundamentals without requiring trichromatic data or knowledge of primary lights.

## Key findings

- Cone fundamentals can be estimated using only dichromatic observer data.
- The method works even when primary lights in experiments are unknown.
- The approach has potential applications in modern image color management.

## Abstract

Two ideas, proposed by Thomas Young and James Clerk Maxwell, form the foundations of colour science: (i) three types of retinal receptors encode light under daytime conditions, and (ii) colour matching experiments establish the critical spectral properties of this encoding. Experimental quantification of these ideas is used in international colour standards. However, for many years, the field did not reach consensus on the spectral properties of the biological substrate of colour matching: the spectral sensitivity of the cone fundamentals. By combining auxiliary data (thresholds, inert pigment analyses), complex calculations, and colour matching from genetically analysed dichromats, the human cone fundamentals have now been standardized. Here, we describe a new computational method to estimate the cone fundamentals using only colour matching from the three types of dichromatic observers. We show that it is not necessary to include data from trichromatic observers in the analysis or to know the primary lights used in the matching experiments. Remarkably, it is even possible to estimate the fundamentals by combining data from experiments using different, unknown primaries. We then suggest how the new method may be applied to colour management in modern image systems.