All the above advice may sound good to a technical person. Aspect ratios and changes etc....Maybe I am not good at understanding all that.
I, too, have the "black borders" on both sides when a photo image is landscape and all sides when photo image is portrait. They pushed Photopad on how to change the background under Tools, but that did not solve the entire problem.
I am a simple retired guy with a new hobby. When the photo image clip shows up in the Clip Preview window with the gray/white checkerboard around it, Why can't those areas just be deleted OR have a way to make the photo fit and cover the entire black area(s)?