Calculating the Diameter of the Field of View at Other Magnifications There is an inverse relationship between the total magnification and the diameter of the field of view-as magnification increases, the diameter of the field decreases in proportion. ? This is the formula for calculating the diameter of an unknown microscope field. This is the formula for calculating the diameter of an unknown microscope field. stage. LPD x LPM / HPM = HPD. This is where math comes in, the values you got earlier for the LPD (1,800 um), LPM (100x) and HPM (400x) can now be used to determine the HPD. Figuring the High Power Field of View (HPD) You can’t use a ruler for HPD, the magnification is way too much. Here’s the formula we’ll use to calculate the HPD. When you want to study a slide under the microscope, you place it on the _____. diameter of field A × total magnification of field A = diameter of field B × total magnification of field B When you want to study a slide under the microscope, you place it on the ________. from Mastering: This is the formula for calculating the diameter of an unknown microscope field. In early microscope objectives, the maximum usable field diameter tended to be about 18 millimeters or considerably less, but with modern plan apochromats and other specialized flat-field objectives, the maximum usable field can sometimes exceed 26 millimeters. At low power on the compound microscope, the diameter of the field of view is 4 millimeters. diameter of field A × total magnification of field A = diameter of field B × total magnification of field B . When in the field of view, the student should calculate the eyepiece divisions, which represents the diameter of the specimen. For instance, the diameter of the specimen here may be 12 divisions. Here, the student may measure the longest and shortest diameter of the specimen in the field of view. This is the formula for calculating the diameter of an unknown microscope field. Field diameter is commonly referred to as “field of view,” meaning that when you look into a microscope, everything that you see falls within that circular scope of vision. You may want to know the sizes of the objects that fall within the circle, and to calculate that you will have to know the size of the field. a) diameter of field A + total magnification of field A = diameter of field B + total magnification of field B b) diameter of field A + diameter of field B = total magnification of field A + total magnification of field B