How to Auto-Blend Layers in Photoshop CS6
The Auto-Blend command in Photoshop Creative Suite 6 helps to smooth out the telltale seams or weird color inconsistencies that occur when stitching together shots with different exposures or contrast settings. You can also use the File→Automate→Photomerge command to stitch together images.
You can also use this command to blend a stack of several images together. For example, say you took several shots, at varying depths of field, of a group of flowers, which caused some flowers to be in focus and others to be blurry. You can blend them together to get a composite shot with all the flowers in focus.
Follow these steps to blend layers:
Create a new document and then open all your source images. With the Move tool, drag and drop each image into the new document.
Each image should be on a separate layer.
Select all the layers and choose Edit→Auto-Align Layers.
Note that you can try to align the layers yourself manually.
Choose a projection method, then click OK.
Select all the layers (avoiding the Background layer, if you have one) and choose Edit→Auto-Blend Layers.
Select your Blend Method — either Panorama or Stack Images.
Select Panorama for, well, panoramic shots. Select Stack Images for non-panoramic images, such as shots of flowers with varying depths of field. Select the Seamless Tones and Colors option to optimize the blending of the multiple images.
Notice that this command automatically applies layer masks to each layer, as necessary. These layer masks attempt to hide under- and overexposed areas.
You can apply this command only on RGB or Grayscale images. You can’t apply it to background layers, Smart Objects or Video layers.