Primotech MAT Instruction Manual page 31

4 Adjusting the Condenser Settings | 4.3 Adjusting the Köhler Illumination
Primotech | Document 430055-9044-008 V.1.0; 03 / 2014
9 Close the aperture diaphragm until the image has the optimal contrast.
This is typically the case when the bright area fills approximately 2/3 of the
field of view.
10 Reinsert the eyepiece.
The sample should now have the highest possible contrast.
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