There's a multitude of emulsions available, even after a lot of them have been discontinued. Each one reacts a little differently to light, both in terms of requiring more or less light, but also in terms of reacting in various unique ways to light.
KODACHROME: 1935-2009(via)
Kodachrome is gone.
More about the end of Kodachrome
As somebody who griped up a storm about Kodak's previous film discontinuations, I have to say that they are discontinuing film with the appropriate amount of respect for our loss this time...