Setup and Bright Field Alignment

12- Adjust aperture iris setting
Each objective (E) has a numerical aperture value (1) engraved on the side. Move the knob (2) on the aperture iris diaphragm (G) to the value corres-ponding to the objective. The iris diaphragm controls the diameter of the cone of light coming through the condenser and the aperture value on the objective provides a perfect depth of field for thin sections. For thick specimens, or whole mounts, decrease the value of the aperture diaphragm to increase the depth of field.With the 100X objective use the highest value on the scale.