`I am really short on time and will have to keep this reply brief. generally speaking, as far as we can know, Friedatheant is correct. That said, when you are dealing with something as brief as an inhaled drag from a cigarette, the time is not long enough for diminishing returns to be an issue. The simple fact is that the longer you hold the smoke in your lungs, the more nicotine and carbon monoxide and, and a few thousand other toxins will be absorbed, and the more tar will be deposited.
Personally, I believe that a smoker should just do whatever feels right and not worry about it. (Okay, if I'm smoking something other than tobacco, I'm going to hold every drag in my lungs as long as Io can, but that's different.' I tend to inhale deeply and pause for several seconds before exhaling, but it is reflexive, not deliberate.
As for the image, it is the qualitative aspect I find rewarding. I believe it does a good ob capturing the subtle nature of smoking's effects and the gradual heightening of the Risk we take.