Jim asked us at the end of class to consider why we have to dot N and L to compute the radiance of a surface caused by a particular source, but we do NOT do the same when calculating the intensity of light visible from a camera (i.e. we do not need to dot N and V). Intuitively, I think this is because as you view a surface from a steeper and steeper angle, the surface is taking up less area in your vision (or less camera pixels) as in Lambert's Law, which means that although the irradiance isn't changing, the radiant flux is. We had to mathematically account for this in the first case because we weren't accounting for the area differential, but in the second case, the surface that you are observing always has the same irradiance, it is just taking up a smaller solid angle in your field of view.
Jim asked us at the end of class to consider why we have to dot N and L to compute the radiance of a surface caused by a particular source, but we do NOT do the same when calculating the intensity of light visible from a camera (i.e. we do not need to dot N and V). Intuitively, I think this is because as you view a surface from a steeper and steeper angle, the surface is taking up less area in your vision (or less camera pixels) as in Lambert's Law, which means that although the irradiance isn't changing, the radiant flux is. We had to mathematically account for this in the first case because we weren't accounting for the area differential, but in the second case, the surface that you are observing always has the same irradiance, it is just taking up a smaller solid angle in your field of view.