Since a familiarity with radiometry, photometry, color science and human vision is necessary to understand this work, this chapter will describe some color science and human vision basics. It would be impossible to cover the whole area of color science or human vision in a single chapter. Many books have been written on the above subjects [WySt82], [Boyn92], [Hunt92], and they are still not completely understood. Therefore, all we want here is to give a brief overview that will help to follow this work successfully.
The way we see objects around us depends on three factors. The first one is light. It is clear that we can not see if there is no light. Most of us have experienced, also, different perception under different lighting conditions (remember ladies checking the clothes colors in front of the shop in the daylight). The second one is the object characteristics itself. Some objects are red, some are blue, etc. The third subject involved in color vision is the human observer. It is impossible to describe the color sensation in our mind. Actually, it is impossible to describe any sensation. All we can say is that some color looks like some other, but this is actually not a description of color. Nevertheless, there is the way of measuring colors, and light, and these methods will be described next. We will start with light measuring (radiometry and photometry), then proceed with colorimetry and finally describe some human vision characteristics that are interesting for tone mapping techniques.