Contribution:Image Handler

Image Handler Support Thread

Image Handler Documentation

Image Handler Site

One of the quirks of Image Handler is that if you want the "zoom" or hover effect or you want watermarks, you must set your Small Image Width and Height to be the same as the Width and Height of Image - Product Listing, Product New Listing, New Products, Featured Products, and Product All Listing.

These settings can all be found in Admin > Configuration > Images.

This is referenced in the support thread.