3.3.5 Aperture Iris Diaphragm
Adjustment
（
Fig.20,21
）
Turn the aperture iris diaphragm lever to adjust the aperture iris diaphragm.
①
•
Generally, setting the aperture iris diaphragm to 70- 80% of the N.A. of the objective in use
will provide an image with good contrast.
•
If the size of the aperture diaphragm minified, the brightness and the resolution declined,
while the contrast and the depth of field increased; In other words, if the size largen, the
brightness and the resolution improved, but the contrast and the depth of field declined.
•
Generally, setting the size of the condenser aperture diaphragm at 70%
～
80% of the
numerical aperture, you can obtain a clear image with enough contrast. If the open of the
aperture diaphragm is too small, the resolution were very low, so please don’t minify the
aperture below 60% of the objective’s numerical aperture unless in a special case, for
instance, observating an almost transparent specimen.
21
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