APPENDIX DExposure and the Digital Linear Effect
Linear vs. Non-Linear
Although the light meters built into digital and film cameras are essentially the same, the way these two processes record and respond to light is different in ways that are important to understand. One simple way to begin looking at this is to consider the graphic systems we use to record the relationship between exposures and print tonalities.
In 1890 the photographic researchers Ferdinand Hurter and Vero Driffield published a seminal paper demonstrating what happened when you plotted exposure and film density on a graph with logarithmic intervals.
If the relationship between light exposure and film density were consistently simple and proportional (or “linear”) ...