Filter Setup - Focus Point


#1

I just pruchased a QSI 683 with filter wheel. I want to make sure I understand the Filter Setup. My understanding is that I should use the Auto-Focus routine to establish the focus point for each filter. (I understand that the temperature should be as constant as possible.) These values are then entered into the “Focus Point” field. Now here is my question: When I switch filters, SGP used the difference between the previous filter and the new filter to calculate a starting point for the new autofocus routine. Thanks for the help.


#2

Robert - I have the same camera. What I do is spend an hour to quickly compare the focus positions for the different filters - before the ambient changes too much. I then make a note of the numbers and put it into the filter focus position table. I use a temperature trigger to kick off an AF run during a sequence and always focus with lum and then get SGP to automatically adjust for the filter. It avoids issues of focusing through narrowband filters.

You can also set it up to take the focus position for the filter as a starting point. Since my image sequences take several weeks, I normally check the focus manually before running the sequence and then let it to its own devices. If the ambient is very different, I might do a quick frame and focus check before running the sequence.


#3

I forgot to mention, when SGP automatically adjusts focus with a filter change, it only makes use of the difference between the filter focus position numbers. In that way, the focus will change with temperature but the delta between filters remain the same.


#4

Exactly what I want to know. Thanks you!


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