Focus Stacking, Part 2: Helicon Focus Pro
September 4, 2014
Focus-stacking promises to achieve the seemingly impossible: creating images with near-infinite depth of field, from the tiniest tundra flower just inches from the lens to the most distant peaks. In part one of my focus-stacking articles, I described the best shooting technique in the field and how to use Photoshop CC 2014 to merge the focus-stacked images. In this blog post I’ll discuss Helicon Focus, a dedicated focus-stacking program that can produce still better results.
Let’s start with the program’s virtues. Helicon Focus offers three different focus-stacking algorithms, labeled simply A, B, and C. Each has its own strengths and weaknesses. The help files offer some general guidance as to which method will work best for particular types of subjects, but the best advice is simply to try all three. Fortunately, the software makes it easy to do so.
The single biggest problem in focus-stacking is the creation of out-of-focus haloes around the edges of sharp foreground objects. In some cases, these haloes are inevitable, because no frame in the focus-stacked series contains sharp image data in the halo region. In the frame focused on the foreground, all of the background is blurry; in the frame focused on the background, all of the background is sharp except the region that is behind the blurry foreground. Unfortunately, that blurry foreground is actually larger than the sharp version of the foreground. Superimpose the sharp foreground on its blurry counterpart, and you’ve got a fuzzy halo around every foreground element. The most problematic subjects are those shot with a telephoto where the region immediately behind the foreground is a long distance away. A tree limb silhouetted against a distant peak is a classic example.
You can control haloes, at least to some extent, by playing around with the radius and smoothing sliders when using methods A and B. Low radius values help preserve fine detail; higher values reduce haloes. Smoothing refers to how the sharp areas in the image are combined. Low values help preserve sharpness but may increase the number of artifacts; higher values reduce artifacts but may also reduce sharpness. These are just general guidelines. You’ll need to experiment with different settings to see what works best for your set of images.
The Pro and Premium versions of Helicon Focus offer retouching tools intended to remove any remaining artifacts. They allow you to clone bits of sharp background into the fuzzy halo regions. The software can even automatically select the sharpest image in the focus stack to use as a cloning source. Although this can work fairly well if the foreground object has a simple shape and smooth contours, it works less well if the foreground elements have complex shapes. The cloning tool doesn’t just sample the sharp background from the source image; if positioned incorrectly, it will clone out-of-focus portions of the source image into the final image. Frankly, most retouching is best done in Photoshop using the Clone Stamp Tool, Healing Brush, or Content Aware Fill. If you really need perfection in a focus-stacked image, use the Quick Selection tool to select the sharp foreground object, invert the selection (so everything is selected except the foreground), then clone sharp background image detail into the blur zone. The selection will protect the sharp foreground, which is outside the selection boundary, so you can’t clone background pixels on top of foreground elements. This is effective but very laborious. It only provides good ROII (return on image-editing investment) when the image is exceptional.
Take a look at the comparison below showing results from a very difficult test case, which I shot with a 111mm lens. I started by using each method in Helicon Focus at the default settings. Method C was the clear winner. Then I began playing around with the radius and smoothing sliders in Method B, and achieved a still better result. As you can see, in this case Helicon Focus beat Photoshop hands down, but it still wasn’t perfect. A little clean-up in Photoshop would remove the remaining artifacts.
Helicon Focus has disadvantages as well. Cost is one consideration. A one-year license for the Lite version, which doesn’t include the cloning tools, batch processing, or Helicon Remote, (software to control your camera when it is tethered to your laptop) costs only $30. The unlimited Pro version, which includes the retouching tools and other goodies, costs $200. Although Helicon Focus processes images faster than Photoshop, you do need to convert your raw files to tiffs before loading them into the program. Don’t hit control-Z to undo when retouching; you’ll crash the program. There’s a bug in the naming algorithm, which is supposed to record the settings you used for radius and smoothing. And while the Lightroom plug-in works, it has some rough edges.
All these problems may well be fixed in the next release. In the meantime, download the trial version and check it out. You may find it allows you to make images that were simply impossible before.
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