Is Image Server Extension needed?

[RandyKreuziger]

I understand mosaic datasets can read in ISDEF files.   Now that Mosaic Datasets are here is their any reason for the Image Server Extension?

[MelanieHarlow]

There is no need to purchase the Image extension and install the stand-alone version to create and publish ISCDefs. However, to publish a mosaic dataset you need the the Image extension for ArcGIS Server. If this sounds confusing, see ArcGIS Server Image extension version 10 versus 9.3.

The online content states:
*NOTE: ArcGIS 10 is the last release of the stand-alone ArcGIS Image Server product. The image service definition (.ISDef) has been replaced by an improved geodatabase data model�??the mosaic dataset�??which can be published as an image service using the ArcGIS Server Image extension.

To migrate, see: Migrating an .ISDef to a mosaic dataset.