About XBlend
XBlend is a Mac OS X front-end for the enblend image blending tool by Andrew Mihal. Enblend uses an intelligent method to vary the way images are blended based on the subject matter. For large, smooth areas such as sky, blending is done over a wide region so there are no sharp changes. For areas having sudden color changes, such as a door frame, images are blended over a narrow area as our minds expect sharp transitions in those areas. Input images are created using the Multi-image tiff option in PTMac or PTBatch then processed using XBlend. Alternatively, enblend can be used directly by PTMac and PTBatch by selecting the Enblend TIFF or Enblend PSD options.

XBlend gives the user a simple interface for using enblend. The user loads the images on the first tab, sets the desired blending options on the second tab and presses the blend button. Two versions of XBlend are available. XBlend 1.2 works with Enblend version 1.3. XBlend 2.1 works with Enblend version 2.1.

More information about enblend can be found here

Here is an example:

Shown below are three images aligned and adjusted using PTMac. Due to a slight light falloff in the lens, you can see seams in the sky when the images are simply laid upon each other. This really is not a great example. Most wide angle lenses have a much more dramatic problem. The seam in the sky disappears when the images are blended using Xblend.

Before: Notice the slight seams in the sky. I will post a better example when I have time.

After: The seams in the sky are automatically blended out. Sharp changes at the bottom are kept intact as the eye expects.