Photomatix is stand-alone software that is used to merge bracketed exposures into High Dynamic Range (HDR) images. Such images have a range of tonalities that exceed what would otherwise be captured by a camera and can be quite useful with high contrast light. But Photomatix can also be used experimentally for non-HDR applications, such as merging two or more images with different subject matter.
(If you are new to HDR, see my tutorial HDR Basics )
For example, in this image of Dance Bliss by artist Marco Cochrane I wanted to have her dancing with herself. This can be accomplished several ways, including using the Apply Image filter in Photoshop. But I did not care for the results that much, so tried merging in Photomatix.
Here is another shot from a different angle. Note that the dancer is in a space that has little detail in the first image.
Using Photomatix, I merged the two images but felt it needed something to indicate motion.
That motion came from an image created by zooming for a 2.5S exposure.
Merging the two versions of Dance Bliss with the zoomed shot produced Dancing Women: