How to Make Selections in Affinity Photo

by | Dec 2, 2020 | Photo Editing Tutorials

Robin Whalley Landscape Photographer

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How to Make Selections in Affinity Photo

One of the most important skills to learn when editing photos is how to make selections. In this tutorial, we look at a real-world example of how to make a selection using Affinity Photo. Selections are a way for you to apply a change to an area of an image (the selection) without affecting other areas. You can also save selections for future use which we will look at later in this tutorial.

Affinity Photo Trial Software

If you don’t have the latest version of Affinity Photo you can download a trial from the Affinity Photo website.

To demonstrate the selection process in Affinity Photo, we will use this image of a mountain. I want to prepare this image for converting to black and white which means I may want to selectively adjust areas.

Initial mountain image before making any selections

I’ve added some lines to the image to indicate the broad selections that I want to create in Affinity Photo. These are the sky, mountains, trees, and water. By creating precise selections for each of these regions we can control the tones and even colours in that area, so improving the final black and white conversion.

Using the Selection Brush Tool

We start by making a rough selection of the sky in Affinity Photo. To do this we will use the Selection Brush which you can find in the Tools Palette on the left of the Photo Persona interface. If you feel confused by the different Affinity Photo Personas see my Personas Explained tutorial.

Affinity Photo Selection Brush

The icon for the Selection Brush Tool looks like a paintbrush with a dotted line around the tip. After selecting this you will see the controls for the Selection Brush displayed in the Context Sensitive Toolbar along the top of the screen. These controls are important to creating a good selection:

  1. The mode buttons allow you to add to or subtract from a selection. Initially we use the Add mode to create the selection. After painting the selection, we may find we have selected areas that we don’t want to include. When this happens, we can use the Subtract mode to paint over these, removing them from the selection.
  2. This section has three options you can use to improve the selections automatically as you paint. We will look at each of these in more detail in a moment.
  3. The Refine button opens the Refine Selections dialog. This is such an important and powerful tool that we cover it in a separate tutorial of its own. The good news is that you can still make excellent selections in Affinity Photo without using it.

To use the Selection Brush Tool, position it over the area of the image that you want to select. Next, click and hold down your mouse button whilst dragging the brush over the area you want to select. As you paint you will see the marching ants appear (animated dotted line) showing the edge of the selection area. How this appears and works depends on the three selection options in the Context Sensitive Toolbar.

Selection Brush Options

You can use the selection options to automatically improve the performance

  • Snap to Edges tries to find an edge in the image where you paint. As you paint over the area you want to select, using this option will expand the selection up to the edges it detects. This helps you avoid needing to paint close to the edge of what you are selecting, reducing your chance of making a mistake. Using this option will speed up the selection process as the selection expands automatically to the edges, limiting your work. The downside is that it may not correctly identify all the edge and you will need to make further adjustments. In practice, be prepared to turn the selection off and on as you work.
  • The All Layers option causes Affinity to sample all the layers in the image for the selection. Typically, images you edit have multiple layers. Using this option allows the Selection Brush to sample all them rather than only one. If you don’t tick this option, only the current layer’s sampled.
  • Using the Soft Edges option creates a slightly soft edge to your selection. This can be helpful in blending adjustments into adjacent areas, but it can also make the selection less precise.

Initially it’s a good idea to have all three of these options turned on. You can then turn them off when/if you identify a problem when working.

Painting the Sky Selection

Now we understand how to use the Selection Brush Tool, let’s use it to paint a selection of the sky in the image.

For this example, we will start in the top left of the sky and paint with the Selection Brush in the Add Mode. This creates a small initial selection surrounded by marching ants. We can then continue to use the brush in the Add mode to add to the existing selection.

Making the initial selection of the sky using the affinity photo selection brush tool

Notice how the selection line has snapped to the bottom of the cloud. This happened automatically as when painting with the “Snap to Edges” option.

It’s a good idea when painting to refine the size of the brush using the [ and ] keys on your keyboard. The [ key decreases the brush size whilst the ] key increases it. You will find that changing the brush size can also affect the precision of the automatic edge selection. When you use a big brush the selection often snaps to only the most obvious edges.

A further tip is to only paint over small section of the image at a time. Paint too widely and you can easily make mistakes by expanding the selection too far. Even then, you are still likely to find areas where the selection doesn’t work properly. Unfortunately, this can be difficult to see when you only rely on the marching ants.

Refining the Selection

Having created the initial selection with the Selection Brush, the best way to find problem areas is using the Quick Mask mode. You will find the Quick Mask icon near to the centre of the Affinity Photo Toolbar (unless someone has moved it). The icon looks like a square with a circle in the centre, and there is a small arrow immediately to the right of this.

quick mask icon in the affinity photo toolbar

When you click the icon to turn on the Quick Mask you will see a red overlay mask appear over the image. This shows the unselected areas and Affinity removes the marching ants’ allowing you to see the selected image areas clearly.

If you don’t see the red mask overlay, you may have one of the other options selected for the Quick Mask. You can access these options by clicking the small arrow immediately to the right of the Quick Mask icon. Click this and you will see a dropdown menu. Select the “Show Mask as Overlay” option from the list then turn off the Quick Mask by clicking the icon again. Now when you turn the Quick Mask back on it will show with the red overlay.

Quick mask mode in affinity photo

Initially the red overlay may appear good, but you need to inspect it closely. When you magnify the image and zoom in to the edge of the mask, you can see the selection problems more clearly.

Close up of the quick mask showing poor seelctions

Here you can see a couple of areas where the selection of the sky has spilled over into the mountain.

To fix these we can switch the Selection Brush Tool into the “Subtract” mode by clicking the button in the Context Sensitive Toolbar. We then paint over the area of the mountain we want to remove from the selection. Remember, the unselected areas show in red whilst the selection is clear. Be sure to paint slowly and below the edge of the mountain.

When tidying up problem areas like this be sure to work at 100% or greater magnification. You should also work with a small brush and only fix small areas at a time.

As you paint and then release the brush, Affinity will try to correct the area by finding the edge. Because you are only working on a small area the Affinity Selection Brush makes a better selection.

Saving the Selection

When you have finished, click the Quick Mask icon again to return to the marching ants view of the selection.

Now rather than immediately adding an Adjustment Layer, take a moment to save the selection in case you want to use it again in the future. You can do this in the Channels Studio Panel.

Affinity Photo Channels Studio Panel

At the bottom of the Channels panel you will see a thumbnail for the “Pixel Selection”. Right-click this with your mouse to display a popup menu where you can select the option to “Create Spare Channel”. Affinity Photo adds the new spare channel to the bottom of the Channels Studio Panel with the name “Spare Channel”.

We can then rename the spare channel to something more useful by right clicking it. Use a name that helps to explain what the channel represents; something like “Sky Selection” will work well.

Whilst we have been doing all of this, the selection has remained in place and we continue to see the marching ants. We can now clear the selection using the “Select” menu. There you will find the option “Deselect” which when clicked clears the marching ants.

Now when you want to apply an adjustment to the sky in this image, you can right click on the “Sky Selection” channel. Then in the popup menu choose “Load to Pixel Selection” and you will see the marching ants appear again. This is how we can store complex selection for future use.

When you save the image in the Affinity Photo format (.afphoto) it also saves and preserves the spare channels.

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Whilst we have only looked at how to create a selection of the sky in this image using Affinity Photo, the process is the same for the other selections. Work carefully using the Selection Brush Tool and its options and you should be able to select most things. The main points to remember are:

  • Start with a broad selection and then refine this using the Add and Subtract modes.
  • Zoom in to a high magnification and work with a small brush to fix problem areas.
  • Use the Quick Mask mode to see what you are doing and identify problem areas.

Although you can achieve a lot using this approach, there are times when you might encounter more difficult problems. When this happens, consider using the “Refine” button in Affinity’s Context Sensitive Toolbar.

More Affinity Photo Tutorials

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

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