The best way to make the calibration better is to use the exact parameters use to range when doing the calibration. So set the ROI and then do the calibration. Offset and Crosstalk. And if you have more than one ROI, do the calibration on both and change the calibration whenever you change the ROI.
In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question. It helps the next guy.
