Difference Vegetation Index
This simple vegetation Index can distinguish between soil and vegetation. However due to its simplicity it does not account for any atmospheric effects or shadows.
The equation is not normalized like many of our other vegetation indices. So resulting values will range from -255 to 255 in the final output.
Reference: Tucker, C. "Red and Photographic Infrared Linear Combinations for Monitoring Vegetation. Remote Sensing of Environment 8 (1979): 127–150.