Over at ProLost, Stu Maschwitz explains clipping, or the inability of AV equipment to display really dark darks and really bright brights:

One of the reasons this subject gets confusing is that it starts with understanding a common topic here on ProLost, that of light’s linearity and how that linearity is remapped for our viewing pleasure. We all know that increasing light by one stop is the same thing as doubling the amount of light. Yet something one stop brighter doesn’t look “twice as bright” to our eyes. We perceive light non-linearly.