Leica M3 Rangefinder Depth of Field Scale on its Summicron Lens barrel

To illustrate DOF for a Flickr contact and why the smallest f-stop gives you another few feet in focus, even though it may not be the sharpest stop (sweet spot) for the lens/image overall.

Expand the image to full size so you can read the scale clearly nearest the camera body.

Focus is centred at about 20 feet (i.e. between the 15 and 25 markers) , and everything on f16 will be in focus from about 10 feet (at the left side of the focus point, opposite the f16 marker) to Infinitiy +, where the right hand side f16 marker is pointing to a spot "beyond" infinity on the scale.