coarse focus and fine focus adjustment focusing knob
Coarse vs Fine Adjustment
difference between coarse and fine adjustment is the range that they have. The coarse adjustment covers the entire range from minimum to maximum. In contrast, the fine adjustment only covers a fraction of the entire range. The bare minimum range for the fine adjustment is the discrete step increment of the coarse adjustment, in order to cover the entire range. It can also be larger, depending on the designer of the device.