The field of view number (FN) is usually engraved on
the eyepiece e.g. 10x/22. The diameter of the visual field of
view can be calculated by dividing FN by the primary magnification
(which is the magnification excluding the eyepiece factor
|The scale in the eyepiece is calibrated,
using a scale of known value as a specimen. Do not change the Zoom
setting without re-calibrating. Align eyepiece scale vertically, to
avoid inaccurate measurements; caused by inclined side to side viewing.
||To ensure the image stays in focus (when
zooming) it is necessary to either adjust the eyepiece tubes or, in some
cases, the focusing eyepieces.
1) Set adjustable
tubes or eyepieces to standard setting.
2) Turn zoom to highest factor and focus on a
specimen; using the microscope focusing.
3) Turn zoom to lowest factor and, if the specimen is
not in focus, re-focus using the eyepiece tubes or the focusing