When outputting to ECW format using the Raster Output operator in a spatial model the output ECW raster image appears more degraded then exporting an ECW raster image with the Export ECW Data tool in ERDAS IMAGINE.
The ECW compressor requires statistics information for the input image in order to scale the compression appropriately. With the Export ECW Data tool this is not a problem because the statistics information is available in the input image file for the ECW SDK to use. However when outputting to ECW format using the Raster Output operator in a spatial model there is no file available yet and therefore no statistics information. So the results of the two methods for creating an ECW raster image will be different.
The solution is to place a Statistics operator immediately prior to the Raster Output operator and have the Raster Output operator fed by the Raster Out port of the Statistics operator. That should provide the necessary statistical information the ECW SDK requires to more effectively compress the output file.
ECW settings (ECW version, compression level, etc.) can be changed in IMAGINE Preference Editor.