This might be a really simple question, but I didn't really start appreciating shoes until recently. I noticed that some AE browns have a "smoked" appearance, which lends to their attractiveness. For example, the Bel Air's have the look: http://www.endless.com/dp/B0015MLXU8...SIN=B0015MLXU8 I also have a pair of Eastons with that smoked appearance too. What causes this? Is it natural in the leather or do they stain it in a particular way?