Answer:
describe how to calculate the field of view
Since the field of view is a circle, the size of the field of view is it's area. You would need to find the diameter of the field of view, using a transparent ruler or a micrometer. Divide the diameter measurement by 2 to get the radius. Then use the formula for the area of a circle, Area = πr2. For example, you measure the diameter of the field of view to be 2.14mm. Divide 2.14mm by 2 to get the radius, and you get 1.07mm. Square 1.07mm, which is 1.14mm2. Multiply x 3.14 (pi), and you get 3.58mm2. So the field of view for this example would be 3.58mm2.
The field of view differs with different magnifications. The lower the magnification, the larger the field of view.