Visual comparison of the objective and con- denser apertures is done as follows: remove an eyepiece from the eyepiece tube, or engage the Bertrand lens by turning the knurled wheel (62.11), (pos. B) and focus with the lever (62.11). Close or open the aperture diaphragm until the image just shows up in the pupil (= brighter circle) of the objective. This is regarded as the standard setting, i. e. condenser aperture = objective aperture.

Replace the eyepiece or disengage the Bertrand lens.

For low-contrast specimens, the aperture dia- phragm can be narrowed further for clearer imaging of fainter structures. In polarisation mi- croscopy, narrowing the aperture diaphragm usually results in stronger colours.

n. b.:

The aperture diaphragm in the illumination light path is not for adjusting image intensity. Only use the brightness adjustment knob or neutral density filters for this.

An aperture diaphragm in the objective is nor- mally opened fully. Narrowing it reduces the intensity and

increases field depth reduces coverslip sensitivity creates a darkfield impression alters contrast

Possible errors

Wrong coverslip thickness or wrong objective. Specimen with coverslip at the top instead of the bottom.

Aperture diaphragm opened too far or closed.

Condenser at wrong height.

Light ring switched in by mistake.

Dirty optics.

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Leica DM IRB manual Replace the eyepiece or disengage the Bertrand lens, Possible errors