Perceptual display calibration

A good display design should make the inaccuracies and limitations of a display technology invisible to the human eye. However, this requires a good understanding of what is and what is not visible to the human eye. For that reason, display engineering is tightly linked to the understanding and modeling of visual perception. Chapter 4 of this book introduced the basic limitations of visual perception that are commonly considered in display design. In this chapter we will take a closer look at selected perceptual models and present a few examples where they are used in practice. As visual models operate on physical units of light, we first need to know how to convert the digital signals driving a display into photometric and colorimetric units. The display models used for such conversion are discussed in Sec. 1. The parameters for such display models can be found either by measuring display characteristics with a colorimeter, or with the help of visual calibration procedures if no measurmenet instruments are available, with the help of visual calibration procedures, discussed in Sec. 2. Once a displayed image is represented in photometric units, it is possible to predict visibility of small contrast patterns using a contrast sensitivity function (CSF). Sec. 3 explains when the CSF is the right visual model for the task and what its limitations are. The last section demonstrates how the CSF can be used to test for and reduce banding artefacts due to limited color channel bit-depth.