Microscopy Podcast

These two microscopic techniques are suitable for different specimens.

The resolution that a microscope is capable of achieving is probably the single most important factor that determines the quality of a microscopic image. Without a sufficiently high resolution, magnification is not possible without loss of quality. There are a variety of different factors that determine the achievable resolution. Some of these factors can not be actively influenced by the microscopist, others can. Some of the factors play a larger role, others a smaller one. In the following post, I want to summarize some of these factors.

Köhler illumination reduces stray light and therefore increases contrast when taking pictures.

Digital photography gives the users many new possibilities in improving photographs taken through the microscope. This post gives an overview of the different image processing functions that can be applied to microscopic images.

Many microscopic specimens are either very thin or transparent or lack color. They lack contrast and can not be easily seen in bright microscope light. In many cases it is not possible or desirable to chemically stain the specimens. In this case, optical techniques become necessary to enhance contrast.

Image editing software can be useful to enhance the contrast of photomicrographs. This article presents a short overview of possible adjustments.

Oblique illumination is a contrast enhancing technique which can be realized with the use of home-made filters (patch stops) placed into the filter holder of the microscope condenser.

Darkfield microscopy is one of the simplest and cheapest contrast enhancing techniques. It works well for specimens that have a refractive index which is different from its surrounding medium, but which are difficult to see because they lack color. Dark field microscopy shows the specimen bright on a dark background.

The condenser aperture diaphragm (or iris diaphragm) is used to control the contrast and resolution of an image. This article explains the usage of the diaphragm.

Koehler illumination offers a range of advantages over “critical illumination”. Illumination is more uniform, specimen heating is reduced as well as light reflections for photographic work.