A man running east on Sixth Street.
Any researcher of brain science will probably tell you that having multiple choices slows thought processes down. When presented with many options the brain would always like to explore them. By the time the exploration is complete, and all the parameters have been locked in, it's a good bet that whatever you were considering doing is now in the immediate past.
I'm not anti-zoom lens. I am not anti-AF. But I have to say that they fail me, in my quest for immediacy, more often than they deliver the goods. I was thinking about that after I shot the photo above. I was walking with a 35mm frame camera with "normal" manual focus lens on the front. I looked up as I was walking down this pedestrian walkway, just east of Whole Foods, and I saw a bald man running towards me. I thought that the repeating pattern of studs and poles that made up the walkway would make for an interesting photograph if I included the runner. I set the camera's focus distance to about 25 feet. The aperture was set to f8.0. My depth of field was wide enough to convincingly include the closer construction features of the temporary structure while getting sharp focus on the runner.
He ran by and I turned, put the camera to my eye and clicked at exactly the spot I wanted.
Now, I am sure that many photographers can set up a camera with fast AF and tracking features, and a zoom lens, and nail a couple hundred decent frames of a scene like this. In the process they will certainly get something akin to the frame I captured. At least I think they will find a close one after they pull their memory card, toss it into the card reader, open Lightroom, and look for the one out of one hundred that they like.
But as they shoot they will go through the process of micro-waffling about which focal length at which to shoot. Then there is the micro-indecision about where exactly to place the point of sharp focus in order to keep everything sharp in the parts of the composition that wants to be sharp -- close and far (hint: it isn't exactly on the back of the runner...). If they are carrying more than one lens there will be a micro-moment of hesitation as they wonder whether or not they really have the right optic on the front of the camera.
It's a process and the more available steps there can be in a process the more likely it is the brain will want to investigate them all. And, even if you are stern with your brain and you have more discipline than an Olympic swimmer, the desire to analyze choices is hardwired into your thinking system and there is a friction of decision that interferes with the ability to react without undue hesitation.
The simpler the system the more streamlined the process. The more streamlined the process the more uncluttered the path is between recognition and action. Perhaps this is why so many of the great documentary photographers of the last century were so happy to find one camera and one lens that resonated with the vision they overlaid on their subjects.
This may be another reason why time spent mastering the many focusing modes of modern uber-cameras might be an even bigger waste of time. But that's just my simplistic approach.