Controlling focus is essential to any shoot, even if that is managed by autofocus systems, and as such, finding the best way to interact with your lens, while maintaining control over the camera, support, and framing, etc, is also needed.
Rather than reaching around to pull focus directly on the lens, follow focus devices have been used for years, either by a solo shooter or by an AC on larger productions. The benefits are clear. Not only are these easier to operate, but the gearing and size of the wheel usually allow for much finer control, which is handy at any time but can be crucial when dealing with a particularly shallow depth of field.
