Focus issues

Hi Shailesh,

I took a look at your SGP logfile with Mikael’s very useful software, SGP Auto Focus LogViewer (see SGP AF Logviewer v1.2 Release ).

In Auto Focus Options you set the following parameters:

AF Run	Data Points		Step Size
  1		    10			   125
  2		    10			   100
  3		     7			   100
  4		     7			   125

Please change the number of DataPoints to 9. There will be no need to modify this value again.

The Step Size that you chose is too low. I estimate that in your case a StepSize of about 175 steps will be appropriate. Assuming that the initial AF curve is symmetric, i.e. the curve is well-centered, the right setting is found when the relation (maximum HFR value / minimum HFR value) is about 4. E.g. if your minimum HFR value is 0.80, the maximum HFR value shall be about 3.20. When this relation is < 4, increase the Step Size. If it is > 4, decrease it. When the appropriate Step Size for your equipment is found, it doesn’t need to be changed again.

One prerequisite to a well-working Auto Focus is that previously you set the focuser backlash appropriately. In SGP you should set this value somewhat larger than the really occurring backlash: the set value must not be smaller than the real value, but it doesn’t hurt if it is somewhat larger.

Bernd