What is the difference between the "Save Image As" and "Save File As" tools in ENVI Classic?

If a dataset is loaded and displayed in ENVI Classic, and the "Save File As" tool is used (from the main menu), the result is a copy of the data file in the format chosen for output. However, if the "Save Image As" tool is invoked (from the display menu), the result is a byte-scaled 1 or 3 band output.

The main reason for the difference in behavior between the image window's File -> Save Image As and the Main Menu's File -> Save File As is that they are actually two completely different tools, with two very different intended uses.

What happens in the main image window's File -> Save Image As tool is that ENVI actually accesses the display values (the RGB 0-255 byte values) and writes out only those values. It's a display capture tool, in a sense. By definition, all of those data values must be byte (8 bit) and all stretching and display effects will be saved. Also, because displays can only contain one or three bands, the output of this tool must also be either one or three bands.

However, the Main Menu's tool File -> Save File As actually writes out the data values, regardless of what has happened in the display. Because the intended use of this tool is to save data for further analyses, it must not change the data values, as this would invalidate any and all downstream work. Accordingly, the Save File As tool can handle data sets with any number of bands.