Konica Minolta DiMAGE Z3 Digital Camera "calculation area circle" Questions

circle area within the middle of image to calculate the exposure. The spot allows precise exposure measurements of a particular object without being influenced by extremely bright or dark areas within

...area of a circle (3.14 x R squared). It may be easier to recall small numbers = equal large openings by thinking of f numbers with a "1/" over them - like this: 1/f1.4, or 1/f2, 1/f2.8, etc. ...