Hi, I have an image, corrected to QuickBird radiance values, that I pan-sharpened. Minimum values in bands 3 and 4, which were close to zero in the multi-spectral image, came up negative in the PC pan-sharpened image. Following up with band ratios produced truly wacky numbers. Has anybody run into this before? Is there a way to constrain the lower values to just over 0? Also, I'm trying to figure out how to get the ratio of incoming and outgoing radiance for QuickBird imagery, not just the outgoing radiance. Can anybody point me in the right direction for info? Thanks, Annie