The need for consistent viewing conditions of prints has been established through the use of light booths conforming to ISO 3664 (ISO 2009), designed to simulate CIE illuminant D50. In particular they are designed to produce the appropriate amount of UV energy to consistently excite fluorescent compounds in the media. For instruments to predict color that will align with the visual perception of samples viewed under ISO 3664 lighting, the source in the instrument must also contain the proper amount of UV energy. ISO 13655 (ISO 2009) refers to such an instrument as having achieved measurement condition M1. Most modern instrument manufacturers have responded to this requirement by either: 1) a single flash method where the UV component is tuned such that measurements match those that would result from an actual D50 source, or 2) a multi-flash numerical method published by Imura (2007 and 2012). The multi-flash method also attempts to match colorimetry that would result from the use of an actual D50 source.
The experiments described here are based upon bispectral measurements of a series of acrylic reference standards representing a range of ISO brightness. These standards have been measured by the NRCC (National Research Council Canada) reference bispectral spectrophotometer. This measurement reports a 2D bispectral matrix that enables the prediction of total radiance factor given any arbitrary incident illuminant. From total radiance factor the color is predicted.