Motic BA210E, Instruction Manual

Page: 18 / 28

17
4.8 Use of aperture diaphragm

The condenser aperture diaphragm is provided for adjusting the numerical aperture (N.A.) of the
illuminating system of the microscope, it decides the resolution of the image, contrast, depth of
focus and brightness.

Stopping down will lower the resolution and brightness but increase the contrast and depth of focus.

An image with appropriate contrast in most cases can be obtained with an aperture diaphragm
closed down to 2/3 of the maximum value.

To adjust the aperture diaphragm:

- adjust the condenser aperture lever referring to the condenser aperture scale, or
- by observing the diaphragm image visible on the exit pupil inside the eyepiece tube, or
- by using a centering telescope after removing one of the eyepieces and focusing on the
aperture diaphragm.

When swinging-out the top lens of the condenser for low magnification objectives, open the
condenser aperture diaphragm completely.
4.9 Brightness and contrast adjustment

Neutral density filters are used for brightness adjustment in routine microscopy and
photomicrography.

For phase contrast and contrast adjustment with black and white film, a Green interference filter
(546nm) is recommended.

An HE (didymium) filter for colour photomicrography, Haematoxylin, Eosin (HE) or Fuchsin stained
specimen with tungsten type film is available.