We’re certainly not the first to entertain this idea, but while most people associate focus stacking with macro photography (at really high magnifications one’s depth of field (DoF) can be 0.05mm, or less) focus stacking can have value in architectural and landscape photography, even product photography as well. It’s something I’ve only recently tried so I thought I’d share some experiences.
For any image there’s one point (at most) in the frame that is in exact focus. Depth of field is the range of distances within any particular image that appear to be in focus. We’re not going to weigh you down with the details, like Circles of Confusion,, etc. There’s more than enough information on that available on the web.
Focus stacking is a process whereby one takes a series of images with different points of focus and then uses software to choose sections of each image to create a composite image. Here’s an example:
This image was made with a Sony A7r III, fitted with a Sony FE 24-105mm G lens. As you can see, the foreground is clearly in focus but the background is not. Shallow DoF can be used as a creative tool in separating a subject from unwanted background elements, but sometimes it’s simply the laws of physics.
Here’s a composite stack of 13 images made with different focus points. The stacking is imperfect (beginner bias) but it’s easy to see there’s a much greater DoF.
So, you’re likely wondering: “Can I do this?” and “What equipment do I need?” The answer to the first question is, “It depends.” It depends on what equipment you have on hand. As with making HDR or panoramic images, there are two phases to images such as this. The first is the collection of the images; the second is stacking and processing the composite. The most important things you need are a subject that doesn’t move and a sturdy tripod. Any movement between images will be noted and show up in the composite. As far as camera equipment, you need at minimum a camera/lens combination that allow you to manually select focus points. NB: Every camera lens has a minimum focusing distance and this process won’t change that. If you’re looking to do macro photography you’ll need to use a macro lens or some device that changes the minimum focusing distance of your existing lens (a bellows unit, extension tubes and the like). There’s also free-lensing, but that’s a topic on its own.
Some cameras (the Nikon D850, the Nikon Z7 and the Phase One XF for example) have this ability built-in to the camera. There’s no reason most other current digital cameras couldn’t add this through a firmware upgrade as it’s a matter of turning the focus barrel of the lens in very precise increments. If you’re using one of the cameras mentioned above, you set up your frame, give the camera the closest focus point, the farthest focus point and the number of steps in between. The camera does the rest. If you’re not using one of those cameras you’re going to have to do it manually, and that depends on the camera you do have. With the Sony A7R III for example, there’s an ability to magnify the frame, either the EVF or the live view screen on the back. Seeing the image magnified makes it easier to determine where to choose a focus point. The Sony also has focus peaking, which shows which areas of the frame are in focus (to some degree). There are DoF calculator apps that will take the lens information, camera sensor information and subject distance and generate a minimum/maximum focusing distance and DoF for any image, but for this exercise I simply erred on the side of caution and made more exposures than I thought I would need. Having a manually-selectable focus point meant I was able to choose different areas in the frame on which to focus.
Having made your exposures, the next step is to download and stack them. The two software packages best known for focus stacking are Helicon Focus and Zerene Stacker, but there are other options. For those who own Photoshop, it’s possible to do focus stacking in Ps. I don’t; I prefer to use Affinity Photo instead. It also has focus-stacking capability. I did download a free trial version of Helicon Focus; I’ll come back to that in a bit.
Recent versions of Capture One software allow you to set an overlay to see which areas of a frame are in focus. This is similar to the focus peaking used in the A7R III and other cameras.
The green overlay in each image shows the areas of each image that are considered in focus. It does this using horizontal contrast detection, so there is likely some bias there. Twelve images are shown here; there were actually thirteen images in this stack, and they combined to show the second image from the top, above.
Here’s another example. I wanted an image of a nurse log and the length of the log exceeds the DoF for this lens.There are 10 images in this stack; again, the green overlays show the areas of each frame that are considered in focus. The stack yielded the following image:
Here the area in focus ranges from the very bottom of the frame to the very top, a distance of some 10-12m. There is some movement in the cedar branch in the upper left, but I included the image to highlight what I meant about having a static subject. What’s worth noting here is that although this image has a very large DoF, it doesn’t look contrived. Our eyes are so quick to move from one point to the next on whatever we place our focus, that seeing an image such as this seems natural.
One last example of another section of the forest.In addition to the three stumps that are the main subject of the images, there are cedar, salmon berry, sword ferns and more in the front of the frame, and Douglas fir trees at the back. Nine images went into making this focus stack. Although I like the colour image, I also converted it to a grayscale image with a slight sepia overtone.
One final note, which is that one cannot be in a hurry to do this work. Each stack takes time to make, from visualizing and creating the composition to choosing the focus points and creating the images for each stack. I was in the woods for about 3½ hours that day and likely walked less than a km in that time. As I mentioned, this was my first foray into focus stacking but I can see how it can have its place in my work.
Okay, that’s it. Now go out and make some images!
P.S. I mentioned that I had downloaded and tried Helicon Focus as well as Affinity Photo. Helicon is a very powerful program, and I didn’t even scratch the surface of it’s capabilities in my limited trial. Having said that, I was both pleased and disappointed in the results I received.
Here the Affinity Photo image is on the left, and the Helicon Focus image is on the right. Both images were created using automatic settings as much as possible and it’s easy to see the loss of detail in the Helicon image. Since both stacks were made from the same 13 base images, the difference must be based on the software’s ability to render the information provided. I’m the first to admit that my results may lie with simply not knowing enough about the software.
Again the Affinity Photo image is on the left, and the Helicon Focus image is on the right. Again, there’s more apparently out of focus area in the Helicon image; at the same time, if you examine the images closely you’ll see that the Helicon image has brought forth more detail in the twig running through the middle of the frame than the Affinity image has.
P.S. II, the sequel: There are some 85 posts on our blog now on digital photography and Lightroom. You can find them all here.