How much light do I need.
Photography is all about finding creative images and importantly creative light. A landscape photographer may have to wait many days for the correct light to appear for his scene.
With street photography the scene is forever changing by the second. Sometimes I have spotted the perfect image, by the time I have lifted the camera to my eye it's no where to be seen.
You can often see the opportunity to click the shutter but on many occasions your minds eye has to quickly decide what the shot is going to look like, particulary if light or lack of it is a major aspect. Unless of course you rely on shot luck. Knowing your camera you quickly set it to acheive the desired result. You may not have more than a few seconds. The scene and its vanishing light are soon gone forever.
Of course the cameras automatic settings will make the decision for you, but then you havn't composed the image. It's therefore not your style. Style is about telling the camera what to do.
Be different - Be creative - Break the rules
The subject is there - The light is right - TAKE THE SHOT