Depth of Focus
The focal depth refers to the depth of the specimen layer which is in sharp focus at the same time, even if the distance between the objective lens and the specimen plane is changed when observing and shooting the specimen plane by microscope. As human eyes are individually different in the ability of their focus adjustment, each person's perception of the focal depth varies.At present, the Berek formula is generally used, because it gives a focal depth value that often coincides with that obtained through experiments.
Focal Depth Formula
Visual Observation (Berek Formula)
Video Camera
In the case of a video camera, the focal depth will vary according to number of pixels of CCD, optical magnification, and numerical aperture. The above-mentioned formula is used as a rough guide only.
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