Looks like dpreview is confused about the naming scheme, though. The 50 AF-1 also adds the feature they say is represented by the AF-2 designation. I think it's just that the increase in guide number "resets" the sub-model count back to one for the 50 AF-1, but since that stayed the same for the 58 model while other things changed, it became the AF-2.
Dpreview describes that feature as "now act as a wireless flash master for cameras without a built-in master", but that's not what the text of the press release says. It appears to be actually a "smart slave" mode, where the remote flash is triggered even without optical wireless TTL. (See their earlier
use of the term "servo mode".)
But from the press relese on Metz's site, that feature may not be implemented for Pentax. It's unclear why it would be brand specific, but the
58 AF-2 press release says "Camera-specific servo flash mode (only for Canon, Nikon, Olympus)". I've e-mailed Metz for clarification.
Anyway, highlights include:
- slightly more power for the lower model
- metal hot-shoe connector, with new fast lock system
- "performance and reliability" improvements
- wider wide-angle diffuser panel
- on the 58 AF-2, wireless sensor moved to the front (!)