Number one reason to stop smoking!
The black is lung cancer and the other is a healthy lung!
Remember! millions of people die a year from lung cancer and even if you don't care what you die from everyone around you (including your children) will take in the same stuff that turns lungs black like this. They will actually take in more because while you are taking your cigarette with a filter- they are taking in everything including what that filter is meant to clean out. Just because you are outside or have the windows down in your car DOESN'T mean that no one else is taking the same smoke.