Spotlight Pro target selection range

[UgashikBob]

When using spotlight pro what has been your experience in the both the distance and target size required to lock on to your selected subject?

 

[tibook]

It seems to change for me all the time. I guess lighting and contrast probably play a big part in it.

 

[UgashikBob]

When using a 12mm lens it requires a much closer range than I expected.