By Dennis Goulet (www.dennisgoulet.us)
Image stacking is a useful tool to combine images to increase apparent depth of field. It can be used for landscapes as well as close up subjects. Several images are made of the same scene with the focus set at different points in the subject. The separate captures are assembled in Photoshop by loading them all as layers of a single image. This example uses a simple stack of two images.
The pink lady slippers were far enough apart that to have all three flowers in focus would require a small aperture of f/16 or f/22. While that would capture all three blossoms in focus, it would also cause the background to be nearly in focus as well. I wanted all three blossoms in focus with the soft effect of the out-of-focus background. The sections of the images below illustrate the capture process; two captures were made at f/8, one with the left flower in focus, one with the flower(s) on the right in focus. The background remains a pleasing blur.
From Lightroom select all the images to be combined, right click and “Open as Layers in Photoshop” from the “Edit In” option.
From Photoshop open Bridge and find the images to be stacked. Select all the images, then from the pull down menu select Tools/Photoshop/Load files into Photoshop Layers. The images will be loaded sequentially as shown in the layer panel below:
Both captures are now loaded into one image as layers. Since the images in the stack have slightly different fields of view due to the change in magnification as a result of changing the focus point, we need to align the elements of the image. Photoshop has a tool for that. Select all the layers (Ctrl-click on each layer) ensuring that they are all highlighted blue, and from the Edit pull down menu, select Auto-Align Layers. A window appears (below) with the alignment options. Since we want each image to be stretched and moved so that all the parts of the image are aligned, select Auto and click OK.
The result after being stretched is that some image layers are larger than others and depending on the composition may require cropping of the stacked image. No point in cropping yet, as it really depends on what the blended image looks like around the edges. With all the layers selected, from the Edit pull down menu, select Auto-Blend Layers. A selection window appears; for this application select Stack Images and click OK. Photoshop will compare each layer and select the sharpest pixel groups and mask out the others. The resulting image may exhibit some anomalies around the edges of the image which can be corrected by cloning or eliminated by cropping.
As can be observed from the resulting masks, the sharpest segments of each image are preserved in the composite image. Unfortunately, there are no adjustments available to control how the software selects the “sharp” segments. As you can see to the right of the flower in the top layer, Photoshop selected some sections of the out-of-focus background to be sharper than the other layer. In this case it does not show in the final image; if it did, the original capture of the bottom layer could be layered with the stacked image and the background segments in the image below masked out.
At this point I flatten the layers to reduce the file size (a 20 layer stack could be 2 GB in size) and save the PSD file with a suitable name. The composite image is now ready for normal editing and enhancement processes.
These image captures were taken in the very early morning while the air was still. Lady slippers will move quite a bit with the least amount of breeze. There was minimum light, the exposure was 1/13 second, so the color was dull. I opted to use Topaz Clarity to add a little snap to the image. When using Topaz Plug-Ins in Photoshop, I always set up a Smart Object layer so that I can return to the plug-in and adjust the settings, especially if I am making additional edits that may affect all or part of the image.
Assuming the stacked image is open in Photoshop, create a copy of the Background layer. The easiest way to accomplish this is to right click on the Background layer and select Duplicate Layer. A dialog box opens and I named the layer to identify it as the Topaz Adjustments layer and clicked OK.
Next, right click on the Topaz adjustment layer and select Convert to Smart Object and then open the Topaz Clarity plug-in from the Filter pull down menu. The Clarity window shows a preview of each preset effect in a collection as the cursor is moved over the preset name, making selection easy. The overall effect can be adjusted with the control bars on the right side of the window. In this case I selected High Contrast and Color Pop 1 from the General Collection to increase the color in the blossoms,. To soften the background I reduced Micro Contrast to -0.40. I also used Topaz Adjust 5 Warm Tone 1 from the Classic Collection of presets to warm the image some.
Dennis Goulet is an amateur photographer located in Massachusetts. A member of Photographic Society of Rhode Island, Dennis concentrates his photographic endeavors on nature and landscape subjects. He is on the Steering Committee of the Massachusetts Camera Naturalists and is a vice-president of the New England Camera Club Council (NECCC). He give presentations on photographic techniques to camera clubs and has presented four times at the NECCC annual conference.
Dennis’ images have appeared in several magazines including Audubon, Nature’s Best Photography, Wild Bird, Birder’s World, Rhode Island Monthly, Outdoor Photographer, and Sierra, as well as on the websites of Audubon and National Wildlife magazine. His image of a Green-breasted Mango was selected Grand Prize Winner of Audubon Magazine’s 2010 Birds-In-Focus photography contest.