... WFC3 Data Handbook > Chapter 6: Charge Transfer Efficiency (CTE) > 6.5 Dealing With CTE Losses In WFC3/UVIS Images . ... Dealing With CTE Losses In WFC3/UVIS Images . ... Another way to minimize CTE losses is to ensure that the background has at least 12 electrons per pixel. ... In images where the predicted background is less than 12 electrons, using the POST-FLASH option is recommended to add enough electrons to get the background counts up to this level. ...