The latest version of MrSID format, MrSID Generation 4 (MG4), supports multibanded or multispectral imagery. Accordingly, Express Server supports multispectral MrSID images as source images. Express Server also supports multispectral source imagery in JPEG 2000 format. Selecting which bands to serve from multispectral images is called band mapping.
The user's browser or other client has no conception of band selection or band mapping. To serve multispectral MrSID images, you must use the Bands element to specify the source bands that Express Server should use to satisfy a request from a client.
The following specifies that the 4th, 2nd and 3rd source bands should be served as the Red, Green and Blue output bands, respectively.
<Bands>4,2,3</Bands>