Research for a new image editing program.
Crop shield is the darkened area around the crop selection / crop area, and can be set in e.g. Adobe Photoshop, Elements, and others.
As far as I understand, these are the defaults:
Adobe Photoshop (& Elements): 75%
Google Picasa: 38%
What do you use? Do you use one setting only? Which one? Or do you vary?