Oil immersion is typically used with the 100x objective lens. However, there are times when using a
50x oil immersion objective lens is helpful. A problem that many users often encounter, is keeping their 40x dry objective from getting oil on it when switching back and forth between the 100x lens and the 40x objective lens. A simple way to solve this problem - and one that is used in many clinical laboratories - is to mount the "dry" 40x objective lens on the opposite side of the nosepiece from the
100x oil immersion objective. This mounting arrangement reduces the likelihood of inadvertently dipping of the 40x "dry" objective into the immersion oil.
 |
| 40x Dry Microscope Objective Lens |
An alternative to avoiding accidentally dipping the 40x dry objective lens into the
immersion oil, is to purchase a 50x oil immersion lens. The 50x oil immersion objective will produce better quality, brighter images than the 40x dry lens does. The disadvantages to purchasing a 50x oil immersion objective lens are that this lens is more expensive than the 40x dry lens, and a 50x oil immersion lens is difficult to use with a haemocytometer because the oil can adhere and inadvertently lift off the
coverslip.
