Focus Stacking In Affinity Photo

Focus stacking is a photographic technique combining multiple images into a single photo. It’s used when a single image can’t capture sufficient depth of field and so doesn’t appear sharp throughout the frame. In this tutorial, I’ll explain how to use Affinity Photo’s Photo Merge feature to automate focus stacking.

What is Focus Stacking?

In some types of photography, like landscape photography, we often want the entire scene to appear sharp and in focus. This in-focus area of the image is referred to as depth of field and is affected by factors like the aperture size, sensor size of the camera, and where we position the point of focus.

Sometimes, it’s impossible to capture sharp images from front to back using a single shot. When this happens, we can shoot multiple images with different focus points. We can then use the focus merge feature in Affinity Photo to focus stack the images into a single image. Doing this allows us to use the optimum aperture for image sharpness and avoid problems like diffraction.

Here, we can see an image on the left created using the focus stacking technique in Affinity Photo. The three source images it was created from are shown to the right of this, numbered 1, 2 and 3.

Shooting Images for Focus Stacking

When shooting images for focus stacking, it’s best to position the camera on a tripod. This ensures each image is identical and only the focus point will change. You should also use a cable or remote release to fire the camera shutter. This will minimise the chance of accidentally moving the camera.

Typically, for landscape photography, we would shoot a sequence of three images. For the first image, we would focus on the foreground. Then, when we take the second image, we focus on the mid-ground in the scene. Then, when we take the third shot, we focus on an object in the distance.

As we are now less concerned about depth of field, this technique allows us to shoot at the sharpest aperture of our lens.

It’s worth mentioning that some cameras have a focus stacking feature. This allows us to set the nearest and furthest points of focus in the image. The camera will then automatically shoot several shots, moving the focus point between each image. How this work does differ from camera to camera, with some cameras allowing more control over the process than others. Some will also merge multiple images into a single RAW file. With others, we need to use special software like Affinity Photo to perform focus stacking and merge the images into a single photo.

The Focus Stacking Feature in Affinity Photo

Having taken our images, each with a different focus point, it’s time to merge them. Before merging them, a helpful tip is to rename the images. That’s because unless you magnify an image, it can be difficult to see where the point of focus was taken.

I recommend adding a number to the start of each file name to indicate its position in the sequence. For example, the first image would be prefixed by the number one, indicating that it’s the closest point of focus. The second image is prefixed by the number two, and then the third image with the number three.

To perform the Focus Stacking in Affinity Photo, click the “File” menu and choose the option “New Focus Merge…”. This will open a new focus merge dialog, which you can see below.

At the bottom of the focus merge dialog, click the add button. This opens a further dialog where you can navigate to the folder holding the images you want to Focus Stack. You can then select and open the images.

Although you can open the images individually, you can also open multiple images together. Hold down the Cmd key on your keyboard, which is the Ctrl key on a Windows PC, and then click the images you want to select.

When you have selected the images for merging, click the Open button. You will then see the selected images added to the “New Focus Merge” dialog, as shown below.

After loading your images, click the OK button at the bottom of the dialog. Affinity Photo will then align the three images to ensure they match exactly. After that, it analyses the images to determine the sharpest areas to use from each. The result is a new image, which can be seen in the Sources panel along with the three images it was created from. You can see a screenshot of this below.

Focus Stacking Problems

Having completed the Focus Stacking to create a merged image, we now need to inspect it for problems. Typically, these will be areas where ghosting appears. You can see two examples indicated in the screenshot below.

The image shows two examples of where movement has caused a ghosting effect.

1. In the first example, we see a moving tree branch which has appeared in different positions in the images. As Affinity Photo decided both images were sharp in this area, they appear in the final merged image.
2. In this second example, the ripples moving on the surface of the water have created the ghosting effect.

We can now use the tools in Affinity Photo to fix these.

Understanding Focus Stacking Problems

Before we look at how to repair the focus stacking problems, we first need to determine the cause. This is where Affinity Photo’s Sources panel helps.

In the panel, we see the three images together with the focus merged image.

At the bottom left of this panel is a small eye icon. We can use this to inspect the individual source images to determine which one should be used at any point in the image. This is probably best illustrated using the ghosting problem in the branches from the top centre of the frame.

The ghosting we see there is caused by the software combining two or more images. If I click on the first image where the focus point is in the foreground and then click the eye icon, I can view that image. You can see this in the screenshot below.

The left image of the two shows the result of the focus stacking magnified at 200%. The image on the right shows the same area but from the source file, where the focus point was in the foreground. Notice how soft this area is in comparison. But this also tells us that the other two images have been merged and are producing the ghosting.

We see the following when we inspect the other two images using the Sources panel.

Notice that the tree branch is in a slightly different position in the two images. Because both images appear to have a reasonable level of focus, Affinity Photo has merged them, which causes the ghosting effect.

If you look closely at the two images, you see that the image on the left isn’t as sharp as on the right. The image on the right is where the focus point was set on the bridge in the distance and is the one we want to use.

Repairing Focus Stacking Problems in Affinity Photo

We now understand what’s causing the focus stacking problem, and we also know that we want to use source image three for the repair.

To fix this problem, turn off the source preview at the bottom left of the Sources panel so that you can see the ghosting. Then click on the source image you want to use for the repair in the Sources panel. In this example, we would click on image number three.

I can now position my mouse pointer over the area I want to repair. As I do this, Affinity Photo shows me a preview of what the repair will look like. This only happens for a couple of seconds once the mouse pointer is stationary. If you want to see the preview for a little longer, move your mouse pointer over the area.

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To repair the ghosting, simply click and paint over the area.

This repair is made using the clone brush tool, which you will see selected in the tools Palette on the left of the interface. If you select a different tool from the tools palette, the Sources panel and/or images vanish. It’s only when you have the clone brush tool selected that you will see the images and can make the repair.

When repairing the problem, Affinity Photo samples the selected area of the chosen image and applies it to the focus merged image. This replaces the existing content in that area. Ordinarily, when using the clone brush tool, you must set the sample point, but this is done automatically when using the Sources panel.

Having completed all the repairs to areas with movement, you should have a high-quality focus-stacked image displaying a sharp focus throughout the frame.

Now Watch My Affinity Photo Focus Stacking Video

In the following video, you can see the focus stacking process demonstrated in Affinity Photo. This uses the same image as the example in this tutorial and includes a few additional tips.

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