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Measuring and Counting with a Light Microscope

Author(s): David R. Caprette, PhD

Measuring and Counting with a Light Microscope

A light microscope allows you to view very small objects, and to collect quantitative information as well. Measurements are made within the microscope's field of view, which is the entire area that you see when you look into the eyepiece. If you know the surface area of a field of view, for example, you can count the number of objects per unit area. Knowing the depth of a sample and the area in view, you can count the number of objects, such as cells in a suspension, per unit volume. Using an ocular measuring device, you can measure the linear dimensions (length and width) of a specimen.

This presentation will discuss how to calibrate a microscope for measurement, how to estimate field diameter, and how to count the number of objects in a single field.  We will cover use of a linear measuring device (called an eyepiece reticule), how to estimate vertical dimensions, and how to use a counting chamber to estimate number of objects per unit volume.