Nikon Eclipse E400 - Magnification and Illumination Control; Condenser Aperture Diaphragm Adjustment; Field Diaphragm Adjustment for Contrast

0 Adjustment of condenser aperture diaphragm
Adjust the diaphragm according to the objective numerical aperture. Turning the condenser aperture diaphragm ring changes
the size of the aperture diaphragm. As the aperture diaphragm is stopped down, brightness reduces and the details of the
specimen become more difficult to see, while contrast and depth of focus increase. Conversely, as the aperture diaphragm is
opened, brightness increases and the details become easier to see, while contrast and depth of focus reduce. It is not possible to
adjust one pair of characteristics without affecting the other. Generally, a well-defined image with appropriate contrast can be
obtained with an aperture setting that is 70% to 80% of the objective numerical aperture. The numerical aperture of each
objective is indicated on the barrel of the objective.
An indication of 40x/0.75 means that the magnification is
40x and the numerical aperture is 0.75.
If the aperture diaphragm is stopped down too far, specimen
5 Magnification: 40x
Numerical aperture: 0.75
details will become difficult to see; therefore, except when
contrast is extremely low such as when viewing a nearly
transparent specimen, do not stop down the aperture to less than
60% of the numerical aperture of the objective.
®@ Adjusting the size of the aperture diaphragm according to the condenser scale
Because the condenser scale indicates the numerical aperture,
adjust the aperture diaphragm ring according to the scale.
<Example> Objective with N.A. 0.75
0.75 x 0.7 (to 0.8) = 0.525 (to 0.6)
Adjust À to this value.
@ Adjusting the size of the aperture diaphragm by using a centering telescope (sold separately)
Remove one of the eyepieces and, using a special adapter (sold separately), mount a centering telescope in its place. Turn the
aperture diaphragm ring to stop down the aperture diaphragm as far as possible. While holding down the flange of the
centering telescope, turn the eyepiece of the telescope to focus on the aperture diaphragm. Turn the aperture diaphragm ring
to adjust the size of the aperture diaphragm. Remove the centering telescope and the adapter, and then reinstall the eyepiece.
Adjustment of field diaphragm
The field diaphragm limits illumination to the area of the
specimen being viewed to prevent excessive light from entering
the view field. Turning the field diaphragm ring changes the
size of the field diaphragm. For normal observation, the size of
the diaphragm should be just outside the edge of the view field.
This adjustment can produce the image with appropriate contrast.