Candid Photography as an Art Form, is I’ll admit part luck but its calculated luck. You put yourself in a place or position that gives you the greatest chance of capturing a subject that suits your eye, or at least comes close to what you’re looking for. If you find something of interest you can’t pose it you have to take it as it is or have the patience of a saint to wait it out until it gives you an opportunity for a reasonable shot. If it’s the type of subject that is movable then you have fractions of a second to compose the shot set the focus and shoot it. If you have the wrong lens at the time or the lighting isn’t the best you don’t have time to change it, you do the best you can with what you have. You can’t control the lighting unless you spend the time to determine when is the best time to get the shot you want with the best lighting. It’s the most frustrating art media I have ever dealt with. To come up with a truly candid artistic photograph you might be lucky if you get the opportunity to come up with one acceptable shot out of hundreds…It is my opinion that a good photographic artist has to have the eyes of an eagle to be able to focus and see its subject at the best angle in order to capture it, the speed of a mongoose avoiding the bite of a cobra, the patience of a saint and the dexterity to utilize their equipment available to them at the moment instantly and correctly.
~Paul Viverito from his article Candid Photography as an Art Form