Brief Tips For Setting Up Darkfield

Switch on power supply and turn to about 4 volts.
Lower condenser slightly and place 1 or 2 drops of immersion oil on top lens.
Place prepared slide on mechanical stage and bring blood into the centre.
Slowly raise the condenser until it touches the underneath of the slide and the light “flares”
Swing the 10x dry objective into the light path and, with the beam splitter in the “100% to eyepieces” position, slowly focus up until the image of the blood film comes into view.
Partially close the field (or base) iris diaphragm and slowly adjust the condenser focus until the image of the diaphragm comes into view.
If the diaphragm image is not in the centre of the field then use the two condenser centring screws (just below the stage) to centre it.
Open diaphragm until it just disappears from view.
Condenser is now centred for the other 2 oil immersion objectives.
Place a drop of immersion oil on top of slide and swing 50x objective into the light path. Use the fine focus to focus as necessary.
Repeat for 100x objective. If the image is too bright and blood film no longer visible simply adjust the objective diaphragm until suitable image is obtained.

Most Common Problems When Setting Up Darkfield…

Insufficient oil on condenser top lens so that full “contact” is not made with the slide.
Likewise for the top of the slide when the 50x and 100x objectives are being used.
Patchy image with bright spots – usually due to small bubbles of air in immersion oil. Slightly lowering and raising the condenser, and/or gently swinging the oil objectives to & fro will often drag the bubbles outside the filed of view.
If no image appears on TV screen check that the beam splitter is pulled out –allowing light to reach the camera.

Highly recommended: constant practice until method becomes second nature.