Generally the condenser is placed in its highest position or just slightly lower. At low magnification objectives (mainly 4x and 10x objectives), the opening of the condenser (or iris) diaphragm should be wide open. For high-dry (40x) and oil-immersion objectives (100x), the diaphragm should be closed slowly while looking at a sharply focused section until the level of illumination is just slightly reduced, in order to attain optimal contrast and resolution.
Low magnification has a greater span of focus compared to high magnification, so it is normal to need to focus if you're increasing magnification. However, if you find that you need to change focus even if going from high to low magnification, try the following (if you can adjust the eye piece):
- Use high magnification and focus on a specimen using the main focus knob.
- Switch to low magnification, and focus using the eye piece adjustment.
If there's a constant visual artifact, even after you've cleaned the eye piece and objective lenses with lens tissue, try raising or lowering the condenser if you can, and the artifact may disappear out of focus.
- Preferably, look up past medical history of the patient, mainly past cancers that could possibly appear in the current specimen.
- Look at each microscopy slide by eye, to plan the microscopy screening so as to not miss peripheral fragments.
- Have a systematic direction of screening through microscopy slides, such as from top left to bottom right as seen in the microscope. When the microscope makes what you see two-way mirrored, the starting position is with the objective pointing at the bottom right of the glass slide.
While learning, you will generally focus relatively more on high magnification features with high specificity, but still have a habit of learning how your cases look at low magnification as well. In time, you will increasingly correlate diseases and conditions with their overall low magnification patterns - patterns that may require 1000 words to describe and thus cannot conveniently be part of written criteria, but will nevertheless allow you to make quicker and more accurate diagnoses.
In microscopy, an artifact is an apparent structural detail that is caused by the processing of the specimen and is thus not a legitimate feature of the specimen. Major artifacts to account for include:
- Patrice F Spitalnik. Histology Laboratory Manual, Vagelos College of Physicians & Surgeons Columbia University. Retrieved on 2021-09-20.
- Taqi, SyedAhmed; Sami, SyedAbdus; Sami, LateefBegum; Zaki, SyedAhmed (2018). "A review of artifacts in histopathology ". Journal of Oral and Maxillofacial Pathology 22 (2): 279. doi:10.4103/jomfp.JOMFP_125_15. ISSN 0973-029X.