I know how to create a transparent background. However, when I use the magic eraser tool, there will always remain little areas or dots of old background. Sometimes they are so small that I only see them when I use the picture in powerpoint. How can I highlight/visualise those little background traces so I can ensure I remove ALL the background?
This can be done with a simple trick.
After you used the magic eraser tool you have to press ctrl and click on the layer you have your background on.
This will make all non transparent areas selected with running ants (Background traces). Now take the eraser brush and delete all the unwanted parts of the background.
To really be sure that you have erased everything, place a solid color filter underneath the layer with the background traces you want to remove, so you can see if there are still some traces visible.