30
70-80%
30-20%
Objective pupil
} In general, the potential resolving power of an objective is fully
utilized if the diaphragm is stopped down to correspond with the
numerical aperture (N.A.) of the objective.
} Depending on the specimen, image contrast or focal depth in ob-
servation or acquisition may be improved by keeping the aperture
iris diaphragm stopped down a little. In general, a good image is
obtained if the diaphragm is stopped down to between 70% and
80% of the N.A. of the objective. Stop further down for less contrasty
specimens.
} To check the position of the perimeter of the aperture iris diaphragm,
remove the eyepieces and look into the eyepiece sleeves to view
the aperture iris diaphragm image and the objective’s exit pupil.
2
Using the Aperture Iris Diaphragm
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