Field curvature is of critical importance in photomicrography because without flat-field correction, the resulting photographs will not have the entire specimen in focus. This Java tutorial explores how changing the microscope focus will affect which part of the specimen remains sharp and clear. To operate the tutorial, use the slider to adjust a simulated focus of the specimen as we would see it in the eyepieces.

The specimen appearing in the simulated eyepiece above is a histological thin section of an elephant toe. As the slider is adjusted toward the top and bottom of the rack, either the center or the periphery of the specimen is brought into focus. The center of the slider rack simulates flat-field correction.