This function is designed to provide fine adjustment to the start position, Step Size and AF Overscan (or backlash) fields. Fine Adjustment runs Autofocus including curve fitting and analyses the result to determine whether or not it can be improved. If so, it adjusts parameters and re-runs. An iterative process is used to home in on parameter values. Here is an example to describe how it works:


Fine Adjustment was run from a starting position of 35,548 with a Step Size of 2544 and AF Overscan of 7477. This is recorded in Run 1 in the results table in the Focus Advisor dialog. The comment column says that the Max/Min Ratio = 1.9 which means that the "Max HFR" / "Min HFR" of the datapoints is 1.9 which could be improved. So Focus Advisor starts Run 2 from position 38,092 with an increased Step Size of 4888 and Overscan of 3738. The Overscan value is reduced here to see if a smaller number would adequately compensate backlash. Run 2 had a Max/Min ratio of 4 which is a little high, and calculated an Overscan value of 8626 so Run 3 was started. Run 3 (which is shown in the V-Curve) started from 38092 with Step Size of 4254 and Overscan of 8626. This resulted in a Max/Min of 3.1 which is good. The datapoints form a V-Curve with no obvious uncorrected backlash (this would show as a flat spot on the right hand side of the curve if there was any). The R2 of the curve fit is 0.999 which is also good so the Fine Adjustment completes after Run 3.