There are various kinds of microscopes. The untrained eye will have a hard time differentiating one from the other because they all have the same purpose - that is to aid in examining a specimen.

Be it hand held or single held, microscopes are important tools in the study of life sciences. Do you remember your biology class when you were asked to carefully examine aquatic samples? That is a preview of things to come (if you chose to continue with the microscopic way of life.)

It is just remarkable that even a simple lens can already reveal what goes on inside the smallest organism. Of course, it still depends on how much light you have, the quality of your lenses, and other microscopic accessories that make it easier for one to observe minute organisms.

The typical bright field microscope extends the resolution of the lenses to the point wherein each magnification is then used in order brighten the subject. The user must then emphasize on where to place the magnification in order to enlarge the specimen. Though enlarging the specimen does not equate to finer and fuller detail. The resolution merely determines the interplaying of the three parts of the bright field microscope: which are the condenser lenses, the objective lenses and the iris.

Even Light has Limitations
Do this exercise. Toss a pebble into a body of water. Notice that the waves slowly move out. This is because the waves bounce from where the pebble hits the water. The reflected and refracted sectioning of these waves then assemble a picture that generate the patterns essential to the liquid.

This is how the hue, contrast and brightness of light are generated. With the reflection and refraction of these elements, the pattern sufficiently creates the light that is needed by the bright field microscope for the user to see the specimen in a better amount of light.

This is where the diaphragm and the condenser of the bright field microscope come in. Expert microscopists know that when the microscope lacks these two parts the subject will not be viewed in the best way.

Therefore, they focus the condensers in such a way that the light source then comes into close focus to the specimen. Once the condenser is adjusted as such, the diaphragm cuts the light that is scattered into the lenses. The flair is then lowered to the contrast and to the degradation of the subject. If the bright field microscope lacks the iris as well as the diaphragm, then the objective lenses won’t be as much help – no matter how powerful the magnification level.

Another function of the bright field microscope
Another function of the iris is to view the objects that are transparent. The aperture reduces the contrast making the specimen stand out from the stage. By reducing the aperture, the resolution is also reduced and the contrast is improved which provides more detail for the subject.

If the slides are stained, it is best if there is a provided contrast. The iris should then cut off the flair. This is done by optimizing the aperture and removing the eyepiece until it appears by the edge of the bright field microscope. As the user looks down on the tube, the specimen is observed better, especially when the iris is wide open.

A technique in examining a specimen with the bright field microscope is through oil immersion. This provides the objective lenses with the highest resolution possible. By replacing the gap between the specimen and the lens with oil, the refractive glass gets the resolution needed in order to eliminate the problems present with regards to light, contrast and hue.

The ultimate resolution depends on the connection of the condenser lenses with the slide. The oil immersion technique permits the bright field microscope to settle on the specimen to be closely observed.

For example, stained bacteria can be visible within the 40x objective lenses. The 100x immersion technique requires the manipulation of the oil so the user must then avoid jamming the edges of the slide. In order to prepare this, the objective lenses must be in the middle of the stage. The 40x objective lenses are then moved away and upwards through the small drop of oil that is added to the specimen.

If the area is dark, it is best that the subject be viewed through the transmitted light which the bright field microscope accumulates through the stained slides.  Dark field provides a different view of the specimen.