I have just started using ENVI and will be analyzing radar data with its PCA algorithm. What is the difference between subsetting an image using ROIs using: a) Resize(spatial/spectral) command on the Basic Tools menu and b) Subset Data via ROIs command on the same menu. The two methods seem to be identical except the latter command (b) also allows you to mask the pixels outside the ROI but in the bounding box. When not using the mask in (b) the results seem to be identical to the former command (a). Is their something I'm missing? Are there cases where one command would be preferred over the other when not masking? Thanks for your help, Orest