Requesting a clear criteria for Bad Focus
Posted: Tue Mar 23, 2010 10:25 am
I stumbled across a calibration movie that made me question my previous criteria for hitting Bad Focus. Looking trough the FAQ and tutorial I have not been able to find a clear answer for what what should be considered Bad Focus. Both are vague, talking about 'deep enough' but not mentioning what 'enough' is, and also some of the example movies in the FAQ do not work.
I tried to search the forums but I failed finding an answer, so here goes a new thread.
The movie in question is this one. Notice how the track is at the very bottom, with the surface just coming into focus at the second bar. For this single movie having the surface in focus in the top 20 % (24 microns) would be an absolute minimum! The surface above the bottom 25 % is the rule me and many other have gone by, but for this movie that is no where near adequate.
Now you may well be able to find the top of the track in another movie and trace it to the next, but it still makes me wonder what we should be aiming for. How deep would we have to go in that movie to find the track leading into this one?
So, how deep must we be able to see for you to feel confident that we do not miss tracks? How many microns below the the lowest point of the surface must be in focus for the movie itslef to be considered In Focus?
I tried to search the forums but I failed finding an answer, so here goes a new thread.
The movie in question is this one. Notice how the track is at the very bottom, with the surface just coming into focus at the second bar. For this single movie having the surface in focus in the top 20 % (24 microns) would be an absolute minimum! The surface above the bottom 25 % is the rule me and many other have gone by, but for this movie that is no where near adequate.
Now you may well be able to find the top of the track in another movie and trace it to the next, but it still makes me wonder what we should be aiming for. How deep would we have to go in that movie to find the track leading into this one?
So, how deep must we be able to see for you to feel confident that we do not miss tracks? How many microns below the the lowest point of the surface must be in focus for the movie itslef to be considered In Focus?