Focusing scale | Article about focusing scale by The Free Dictionary
focusing scale[′fō·kəs·iŋ ‚skāl]
A graduated scale to indicate appropriate lens-to-image plane positions for given lens-to-object plane distances.
References in periodicals archive
Equally attractive for astrophotography is the FLT-98's built-in digital focusing scale
(called the Digital Display Gauge, or DDG for short) and $269 optional Adjustable Flattener Reducer IV (AFR-IV).
The other is that the lens's focusing scale is much too crude for you to judge the small adjustments you make.
One is a focusing scale and the other a clever mechanism that changes the focus of his Canon 300-mm f/4 lens by very small, controllable amounts.