Align and Blend Layers
Photoshop can transform multiple layers to align matching content in those layers. This is particularly useful when used in conjunction with another feature for blending the content in layers to maximize the sharpness throughout an image, increasing the depth of field. This technique is also known as focus stacking, and with it you can create images with a sharpness that is very difficult or impossible to achieve otherwise (FIGURE 15.25).
FIGURE 15.25 The three source images. Note the limited depth of field and how a different avocado is in focus in each one.
To merge multiple image files into one layered file, you can take advantage of automation features in Photoshop or Adobe Bridge. Note that when you use raw files in Adobe Bridge as your source, the current develop settings will be applied.
While it’s not a requirement, you will usually get the best results if your source images are of stationary objects and were taken with a tripod.
To align and blend layers:
Do one of the following:
In Adobe Bridge, select the images you want to blend and choose Tools > Photoshop > Load Files into Photoshop Layers.
In Photoshop, choose File > Scripts > Load Files Into Stack. Use the Load Layers dialog to navigate to the files you want and choose them.
A new Photoshop file will be created containing separate layers with the name and content from each source image (FIGURE 15.26).
FIGURE 15.26 The new layered Photoshop file
On the Layers panel, Shift-click all layers to select them.
Choose Edit > Auto-Align Layers. In the dialog, for Projection, choose Auto and click OK.
Choose Edit > Auto-Blend Layers. In the dialog, for Blend Method, choose Stack Images and click OK.
Photoshop finds the areas of maximum sharpness and applies layer masks to reveal those areas in each source layer (FIGURE 15.27). Additionally, Photoshop creates a new merged layer combining the unmasked areas of the source layers on top of the layer stack (FIGURE 15.28).
FIGURE 15.27 Out-of-focus areas in each source image layer are masked out.
FIGURE 15.28 The topmost merged layer with increased depth of field