Last summer when we were in Maine one of the people staying at the B&B with us was also a photographer. Over breakfast one morning he told me about image focus stacking. The technique is similar to HDR photography, but instead of exposure, different images with various focus and depth of field are combined. Several shots are taken at various focal lengths, and the images are “stacked”, taking the best focused areas from each image to create a very sharp final image.
When I got home from Maine I downloaded Keith’s Image Stacker . Keith Wiley does astrophotography, and wrote the software to sharpen some of his images. I know some people who have gotten excellent results from his program, but I just couldn’t seem to get the hang of it. I lost interest. Last week I upgraded to Photoshop CS5, which has built-in image stacking, and my interest was renewed.
This technique works best where you would traditionally have a narrow depth of field, such as macro work, working with large apertures, or working with a telephoto lens. I always take photos of of cone flowers about this time of year, and I thought they would be the ideal candidate to try out all three of these. The flowers are complex, and it’s often hard to get the entire flower in focus.
I started with my 50mm f/1.8 and added three close-up lenses for macro work. My intent was to reduce DOF as much as possible, so I opened the aperture wide open. Of course, I had to use a tripod for consistent shots, and I used full manual mode so that exposures would be the same for all shots. In this case I took three shots with different parts of the flower in focus.
I loaded them into Photoshop using Photomerge, which also aligns the images and loads them into a single Photoshop file as layers. I then selected all the layers, selected Auto-Blending from the Edit menu, then photo stacking. Photoshop did the rest, taking the sharpest bits from all three images. Here’s the result:
Not so great, huh? As it turns out, three shots was probably not enough to really create a sharp image. You wind up with portions of the shot that are still blurred.
This next one was a composite of five shots, and turned out a bit better, but still has some blurred areas.
I finally just started clicking away, trying to make sure I had the entire flower in focus for this shot of foxglove. I ultimately picked nine shots from the ones I snapped to create the composite.
The shot at the top of the page was composed of ten images, and is my favorite so far. For this one I switched from my 50mm to my 200mm to create the narrow DOF.
I learned a little trick as I did this. I wound up with dozens of shots of the same flower. These all looked similar, and I wasn’t sure which shots belonged to the same series. I started sticking my hand in front of the camera and snapping a shot of my fingers to indicate when the next series began.
This process preserves what I like about having a narrow depth of field – bokeh and an indistinct background – while also increasing sharpness for the main point of interest. I want to try it with some more subjects. There’s supposed to be a full moon this weekend, and I may try it on some astrophotography with my Celestron telescope, like Keith Wiley suggests. Regardless, it’s another cool tool to add to my photography arsenal.