The No.1 Sharpening Mistake in Affinity Photo

When you’ve finished editing a photo and you are ready to sharpen it, there’s a common mistake that you need to avoid. This mistake doesn’t have a name to describe it, but it can easily cause you to over or under sharpen your photos. You probably don’t even realise you are making it; and in case Photoshop users are feeling left out, they also regularly make the same mistake.

In this article, I’m going to explain this mistake and how you can easily avoid it by using a simple technique. Let’s start with a simple example, sharpening a landscape photo using the Unsharp Mask Filter in Affinity Photo.

Adding the Unsharp Mask in Affinity Photo

After opening the image to sharpen in Affinity Photo, add an Unsharp Mask Live Filter to it. You do this in the “Layer” menu by selecting “New Live Filter Layer”. This displays a list of filter categories in a sub-menu where you select “Sharpening” and then the “Unsharp Mask” option.

You will now see the new Unsharp Mask Live Filter added to the Layers Studio Panel and the Live Unsharp Mask dialog opens.

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The new Live Filter will either be attached to an existing layer or above it. This depends on how you have Affinity Photo configured. I prefer to have the Unsharp Mask sharpening layer on its own, above the other layers.  This reduces the chance of making a mistake. If yours is attached to another layer, you can click and drag it using your mouse to move it to the top.

There are a few reasons that we are using a Live Filter to sharpen the image and not a regular filter:

1. It’s non-destructive because it isn’t applied directly to the image pixels.
2. Because it’s non-destructive, we can continue to refine the sharpening as well as use masks to make localise adjustments.
3. You can’t use the technique that I’m going to share with a regular filter. You need to be using a Live Filter for this to work.

Now whenever you have the Unsharp Mask Live Filter selected in the Layers Studio Panel, you will see its dialog displayed. This has three controls which we can use to apply sharpening to our photo.

The Sharpening Controls and What They Do

The two Unsharp Mask controls that we will be using are Radius and Factor. We don’t need to bother with Threshold for this demonstration, but you would use it when sharpening for the best results.

The Unsharp Mask works by increasing the contrast of pixels along the edges of objects in a photo. When we increase their contrast, it makes dark pixels darker and light pixels lighter. This is what makes the edge easier to see and produces the sharpening effect.

The Factor slider is what we use to control how much contrast is applied to the pixels being sharpened. The higher the values used, the greater the contrast enhancement and sharpening that’s applied.

The Radius slider then controls how wide an area is affected by the sharpening. The reason that this is a Radius setting is that when we sharpen an edge, we affect both sides of the edge.

Now let’s look at a couple of common problems.

Sharpening Problems in Affinity Photo

Look at the following three samples showing a section of an image magnified to 150%.

The images have three levels of sharpening applied to them using Affinity Photo’s Unsharp Mask. They are:

1. No Sharpening.
2. Radius = 1px and Factor = 1
3. Radius = 1px and Factor = 4

Comparing sample 1 to sample 2, sample 2 appears only slightly sharper. Now comparing it to sample 3, sample 3 appears much sharper but is probably too sharp. If you look at the hill on the horizon in sample 3, you can see a thin light edge above it and a dark edge below it. This is called a sharpening halo.

Whilst we need sharpening halos to produce the sharpening effect, we don’t want them to be obvious like this. When the sharpening halo becomes obvious the image will begin to appear ugly.

In sample 3, the halo is noticeable but not immediately obvious unless you know what to look for. But look what happens when we increase the Radius slider to 5 pixels. It looks extremely ugly, and anyone will notice the effect.

The way that we can control the sharpening halo is by reducing the Radius and Factor sliders. But then, we run into a big sharpening problem.

The Big Sharpening Problem

The big sharpening problem that we face is that some areas of an image will require more sharpening than others. Look at the following example which demonstrates the issue with image sharpening.

All three samples are shown at 100% magnification and have the same Unsharp Mask settings applied. Here are the problems:

1. There is a halo on the hill.
2. This entire area appears over sharpened with obvious halos around most of the objects.
3. The green grass appears well sharpened in this sample, but we can see halos around the lighter grass.

What’s causing this “uneven sharpening” problem isn’t the level of detail in the image, it’s the tonal range the sharpening is applied to. The sharpening that’s applied to lighter pixels tends to be easier to see and the same is true to some degree for darker pixels.

Look back to sample 2 again. The reason it appears so over sharpened is that the image has a lot of highlights in this area. Now compare this to sample 3 where only the lighter blades of grass appear overly sharp. The grass in the midtones is fine.

To improve our sharpening and fix this problem, we need to apply more sharpening to the midtones of the image, and less to the highlights and shadows.

The Affinity Photo Sharpening Fix

Fortunately, there is a simple fix that we can use to correct this problem and improve our image sharpening. It’s called the Blend Options control. You can access it by clicking the small cog icon to the top right of the Layers Studio Panel.

After clicking the cog icon, the Blend Options dialog opens.

This dialog allows us to control how the selected layer (the Unsharp Mask Live Filter) affects the other layers. We can do this by adjusting the control line in the “Source Layer Ranges” grid.

In the following screenshot, you can see the shape of the control line that allows us to sharpen the midtones without affecting the lightest or darkest pixels.

You can also see the effect that this has on the sharpening applied to the grass. This uses the same settings for the Unsharp Mask that previously caused the lighter grass to appear too sharp.

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How the Blend Options Control Works

To understand more about the sharpening problem and how the Blend Options dialog works watch this short video.

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You can also watch this video on my YouTube channel. I publish a new video every week, often based on subscribers’ requests and feedback. Subscribe to my YouTube channel now and be sure not to miss future videos.

In addition to the video, you can learn more about the Blend Options, or Blend Ranges as they were called, by reading my introductory article. Although it’s based on Affinity Photo v1, it’s the same in v2 and is a helpful one to read next.

More Affinity Photo Tutorials

You’ll find more high quality, free tutorials on my Affinity Photo Tutorials page.