Compression Preferences

You can access the Compression Preferences by selecting "Preferences..." from the "Edit" menu, and then clicking on the "Compression" tab.

This screen lets you choose the default compression method.  This will be used for all files added to an archive, and will be the default choice when you ask CiderPress to re-compress files.  It's also used by the disk image conversion tools.

The compression algorithms are described in detail here.