I recently acquired a Honeywell Pentax 1/21 Degree spot meter. It is in excellent shape, however I didn't receive a manual with it. I need t know how to tell if it is on high or low. also there is a white button on the side which seems to eleminate a filter in the viewfinder????What does this do??? also some figures on h exposure wheel I don't understand.........Some help here would be very much recieved..Thanks in advance.........Gary (-: