1. A focus assessment method for determining a focus classification for a workpiece feature image, the focus classification usable to determine whether the image is sufficiently focused, such that a machine vision inspection system may perform useful machine vision inspection operations on the workpiece feature image, the method comprising: acquiring a first image of a workpiece feature for which an image focus classification is to be determined; determining a plurality of focus classification features based on the first image; and determining the focus classification based on processing the determined plurality of focus classification features using at least one classifier, wherein: the at least one classifier comprises at least a first respective classifier that operates on a first respective plurality of classification features; and the focus assessment method does not require the acquisition of an additional image of the workpiece feature that is differently focused than the first image.