Using the Affinity Photo Unsharp Mask Filter
In this tutorial, I’m going to explain how to sharpen a photo with the Unsharp Mask filter in Affinity Photo Desktop. I’ll cover what the different sliders do in the Unsharp Mask and how you can use these to improve your sharpening results. This means you’ll achieve much sharper photographs but also cleaner images with fewer sharpening problems.
You can see the image I’ll be using to demonstrate the sharpening workflow below.
Controls in the Unsharp Mask Filter
The Affinity Photo Unsharp Mask filter only has three controls which you can see in the screenshot below.
The controls are:
But to understand what these are doing and how best to use them, you first need to understand a little about how sharpening works.
How Sharpening Works
Sharpening is an optical illusion. It works by finding the edges in an image and then enhancing the contrast of these. This makes the edge appear more obvious and clearer. By making all the edges and fine details clearer the image appears sharper. You can see how this works using something called a sharpening wedge like the image below.
The sharpening wedge is just two gradients running in opposite directions, next to each other. Notice each gradient appears well defined at either end but less so in the centre. This is because, at either end, there’s a large difference between the tones in each wedge. There you see black next to white which is easy to distinguish between. If you move to the centre, the gradients show similar shades of grey making it less easy to see the edge. If we can increase the contrast between the gradients along the edge where they meet, it helps separate the two. This is what sharpening does and you can see an example below.
Let’s look at how the controls in the Unsharp Mask affect the sharpening wedge.
Unsharp Mask Controls
We said earlier that sharpening works by enhancing the edges in an image. It does this by increasing the contrast along these edges. This means that dark grey pixels become darker and eventually black. At the same time, light grey pixels become lighter and eventually white. You can control the contrast adjustment applied to the edge using the “Factor” slider in the Unsharp Mask Filter. The higher the Factor slider the stronger this contrast adjustment is.
The Radius slider is also important in helping to make the sharpening effect visible. It controls how wide an area sharpening’s applied to. The higher the Radius the wider the sharpening edge, making it easier to see. If you apply too small a Radius you won’t be able to see the sharpening effect but if the Radius is too wide the edge becomes visible. When the edge becomes visible it’s often called a sharpening halo. You should try to avoid visible sharpening halos for good sharpening.
Here you can see a high Factor setting applied using a Radius of 7 below.
Notice the edge between the two gradients is wide and very clear to see. In fact, it’s so wide that it looks like someone has drawn a thick line along each edge of the gradient.
The third control in the Affinity Photo Unsharp Mask filter is Threshold. This determines where there’s an edge in the image by comparing adjacent pixels. When you compare two pixels next to each other and one is brighter than the other, it indicates the pixels are part of an edge. The greater the difference between the two pixels, the clearer the edge will be. The Threshold slider controls how large this contrast difference needs to be before Affinity Photo detects an edge to sharpen.
Using a low Threshold setting, it only needs a small difference between adjacent pixels to detect an edge for sharpening. All the sharpening examples above used a Threshold setting of 0. Therefore, you see the effect along the entire length of the gradient. But look at what happens when we increase the Threshold.
Now we’re not sharpening the centre part of the wedge there’s less of an impact in the other areas.
By controlling these three sliders you can increase and reduce the sharpening effect as well as control sharpening halos.
Sharpening Workflow in Affinity Photo
Let’s look now at what we need to do to sharpen our example photo.
Typically, you would apply the Unsharp Mask filter after you’ve finished adjusting the image. That’s because the adjustment you make in Affinity Photo might affect the sharpness.
Once you’re ready to sharpen your image, create a new layer to apply the sharpening too. This layer should be a consolidated copy of all the other layers in the image. You can create this layer by clicking the top layer in your Layers Studio Panel and pressing Shift + Option + Cmd +E (on a Mac) or Shift + Ctrl + Alt +E (on a PC). You’ll see the new layer appear at the top of the other layers. Click this layer to select it.
Now select “Layer | New Live Filter Layer | Sharpen | Unsharp Mask…” from the Affinity Photo menu. This adds the Unsharp Mask Filter to the new layer you created, as a Live Filter. You could also apply the Unsharp Mask Filter directly to the new image layer using the Filters menu. This still works but it’s better to use a Live Filter because you can make further adjustments later.
You should now see the Unsharp Mask filter dialog where you can adjust the controls we discussed above.
Here’s a close-up section of the image magnified to 100% showing before and after the unsharp mask.
Notice the result is subtle but the image appears sharper. It’s also helpful to magnify your image at 100% when sharpening and view an area with lots of details. This can help you judge the sharpening effect as you adjust the controls.
In this tutorial, we’ve examined how sharpening works and how to use the controls in the Affinity Photo Unsharp Mask Filter. We’ve also covered how best to apply the Unsharp Mask filter. Try to avoid applying the filter from the Filter menu as this is a destructive edit that’s applied directly to an image. It’s better to apply a Live Filter to a new layer created for the purpose of sharpening.
If you follow these steps, you’ll soon be producing excellent results with the Affinity’s Unsharp Mask filter.