Microscope Depth of Field

Microscope depth of field is measured from above and below the focus plane that provides an acceptably in-focus image. The lower magnifications tend to have a larger depth of field. Additionally, a higher numerical aperture will have a shallower depth of field.


The image above is a good example of varying depths of field. The metal under the microscope has an indented strip (where the Microscope World text is in the image) that is not in focus. This is because it is out of the range of the in-focus depth of field. If you were to change the focus on the microscope so the darker strip was in focus, then the outer edges would become out of focus.