A zoom lens includes a first lens group having a negative refractive power, and second and third lens groups each having a positive refractive power, sequentially aligned from an object side. A reflector is pivotally installed in a body case. The computer program displays a label template adapted to receive a plurality of data fields inputted by a user therein, wherein each data field is adapted to receive and display respective data. A first exponentiation part calculates u\u2032=ua.