Spray and Pray
There are some occasions where a DSLR and zoom lens can bring you unwanted attention. Basically, if you bring the camera up to your eye, everyone becomes self-aware and changes their behavior. Here in New York, the authorities can get a bit edgy when taking their photo. Of course it's not illegal, but since Obama was in town, tensions were already high, and I wanted to avoid any confrontations.
When I saw this particular scene of three lounging traffic cops near 34th street, I wanted to capture them just as they were. I used the "spray and pray" technique. If you've never heard of it, let me explain how it works. I start by setting the camera to the high speed burst mode, and select the center point for autofocus. I then set my exposure manually, and the lens at it's widest focal length. In this case, it was a 17-40mm @ 17mm. A wide angle lens is an important consideration here, as they inherently have greater depth of field even at wider apertures. With all my settings arranged, I walk by slowly without looking at the subjects and hold the shutter down. The camera is down by my hip so I don't know what it's seeing. As I pass, I fire a dozen or more shots in a few seconds. If timed correctly, the autofocus will lock onto the subject in the center of the frame, and everything else will fall into place. That covers the "Spray" portion of the technique. Now, for the praying...
After you take shots in this manner, just keep moving quickly until you're well out of sight. You may have something great, or you could have a bunch of terribly out of focus pictures of your feet. I know this isn't the most precise technique, and the percentage for keepers goes way down. However, in my opinion, it's better than leaving the camera in your bag because you were afraid of the consequences. Next time you're in a tight situation, give it a try.