Adjusting the aperture diaphragm

Rotate the condenser aperture diaphragm ring and the size of the aperture changes. If the aperture is reduced then the illumination decreases, fine detail becomes difficult to see, contrast is increased, and the area of focus deepens. If the aperture is opened then the illumination increases, fine detail becomes easier to see, contrast is decreased, and the area of focus becomes shallower.

Generally, if the aperture is closed to 70-80% of the numerical aperture of the objective then a clear image with reasonable contrast will be obtained. Also, the aperture diaphragm is used to adjust the numerical aperture of the illumination light, not the brightness. To adjust the brightness, the brightness adjuster is used.

• It is possible to see the actual aperture condition by removing the eyepiece and looking down the eyepiece tube. (sometimes the eyepiece is fixed to the eyepiece tube with screws. In this case first loosen the screws before removing the eyepiece)