Question:

I have a TiX580 and with using the filter mode I do not see improvement in thermal sensitivity. 

Answer: 

         The TiX580 has indeed a Filter-mode that can bring some additional improvements. 
         One of them is improved thermal sensitivity ( NETD) , this is improved from 50 mK to 30 mK when filter mode is switched on.  
         

However in 2019 there has been a change in sensor hardware;
 

The sensor resolution changed from 324x240 to 640x480, and while the huge benefit of getting more image resolution, it had an additional consequence of the thermal sensitivity no longer being able to improve to 30 mK. 
The TiX580 camera's of 2019 and later will not have the benefit of 30 mK in filter-mode, but just the specified sensitivity of 50 mK.  
 

Upon checking see the first 4 digits of the serial number, these are standing for year and week number of production. 
All TiX580 starting with 1901xxxx and newer camera's have the new higher resolution sensor. 

Author: Martijn Gerlag