Hydra gives human eye perception to your photographs by allowing you to create high dynamic range (HDR) images from a series of regular photographs, either from DSLRs or traditional point-and-shoot cameras.
Improved Image Pipeline, RAW, DNG, OpenEXR Support
Hydra can import RAW file formats from most cameras (same as Aperture). A full list of supported cameras can be found there. If your camera is not supported, you can use Adobe DNG Converter, which will convert your images to the digital negative format that can then be imported into Hydra.
Hydra pipeline improved a lot as of version 1.5. It now builds a full 32-bit per component high dynamic range image and provides OpenEXR export format to further edit the image in other applications. Moreover, 2 Tone Mapping techniques are now available (Highlights Compression, Local Adaptation).
Hydra talks with Aperture. You can directly import image from Aperture, or export to Aperture (and the same for iPhoto of course). But there's more. Hydra is now available as an Aperture PlugIn (Beta). You can now create HDR images right from within Aperture.