When the planes of the array of images are aligned, There are always a few columns and rows at the edges of the image for which there is incomplete data. Most post processing (Mosaic assembly, NDVI) overlooks the missing data, but sometimes results may be affected.

By reducing the final field of view slightly (effectively scaling up the final images) the edge effects disappear.

Reducing the field of view can also help reduce lens distortion effects, which happen typically at the edges of the image where the lens is less efficient.

A value of 0 leaves the image intact. A positive value reduces the field of view by the percentage it represents. '1' means that the field of view will be reduced by 1%. Typical values range from 1% to 10%.