Strategies for Resolving Camera Metamers Using 3+1 Channel

Abstract

This paper discusses the problem of reducing camera metamerism by using a fourth spectral channel in addition to the typical red, green, and blue channels of the tristimulus sensor used in the commercial consumer cameras. Specifically, we consider three options for this fourth channel. The first option is to use a color channel from another camera to reduce metamerism. The second option is to use a color channel from an image captured by the same camera but with a color filter as the fourth channel. The third option is to design a specific spectral channel to be fabricated with the existing camera sensor. This option uses the metameric black space to design the channel. The commercial cameras' original metamerism is typically more than 20%, as observed in a dataset of 335 spectral images captured in 5 different indoor illuminations. Our results show that the third option is the best since it reduces metamerism down to about 5%. Among the first and second options, the first option is more effective and it reduces metamerism down to about 15%. The channel designed using the third option can be used for advanced applications such as distinguishing objects with different spectral reflectances but similar colors.