Replace a lacklustre sky in Affinity Photo: how to transform your landscape shots

Affinity Photo replace skies
(Image credit: James Paterson)

Watch video: How to replace a sky in Affinity Photo

Whether you want to drop in a new sky to improve a landscape or blend two shots, Affinity has excellent tools for compositing images. The first stage in any compositing project is to isolate part of an image, like our sky. This is a complicated shape, and selecting it freehand could take hours. But, thankfully, Affinity has a tool that does it in seconds.

The Selection Brush has a ‘Snap to edges’ feature that helps it seek out changes in colour or contrast. So, by painting the sky here with the tool, it’ll snap on to the edges of the horizon.

Once the area is isolated, the next step is to improve the selection. Initially it’ll be hard and jagged, but if we run the Refine command we can get a neater, more precise edge, one that picks out the gaps and bits of sky that we may have missed along the horizon (see box).

After this, we can use the command to convert the selection to a layer mask. A mask will hide everything outside of the selected area, so the original sky gets hidden. But the great thing about masks is that they’re editable, so we can zoom in close and fine-tune the edges by painting with black or white over the image. Finally, all we have to do is drop in the new sky to complete our scene.

Read more:

• Affinity Photo 1.8 review

Step 1: Select the land

You can click on the gadget in the top right corner of these screenshots to zoom in on a full size version. (Image credit: James Paterson)
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Start by open your landscape shot into Affinity Photo. Grab the Selection Brush from the toolbar and check ‘Snap to edges’ in the options at the top. Paint over the land (not the sky) to select it. If the selection includes unwanted areas, check Subtract at top left and paint to remove them. You can resize the brush tip with the ] and [ keys as you paint.

Step 2: Refine the edge

(Image credit: James Paterson)
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Click the Refine button at the top. Set Border Width to about 2% to control the area of refinement along the edge (this will depend on your photo). Using the Adjustment Brush within the command, paint over any areas of your photo on the horizon line to direct the command to parts of the edge that need that little bit more refinement.

Step 3: Improve the selection

(Image credit: James Paterson)
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The Adjustment Brush in the Refine command has buttons for Foreground and Background. These let you fine-tune edges by telling the command what is foreground (the land ) and which is the background (the sky). Use the brush to paint over parts of the edge that aren’t perfect. You might want to experiment with different overlays.

Step 4: Drop in a sky

(Image credit: James Paterson)
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Now set Output: Mask and hit Apply. Choose a 'sky' image you want to drop in, then press Cmd/Ctrl+A to Select All, Cmd/Ctrl+C to copy, then go to the other image and press Cmd/Ctrl+V to paste. Go to the Layers panel and drag the sky layer below the other. Grab the Move tool and position and resize the sky to fit.

Step 5: Perfect the mask

(Image credit: James Paterson)
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Highlight the mask on the top layer, then zoom in close to the horizon to check that the edge is perfect. Grab the Brush tool and, if needed, paint with black to hide parts of the layer, or white to reveal hidden areas (you can press X to switch between black and white while painting).

Step 6: Tonal tweaks

(Image credit: James Paterson)
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Finally, we’ll add a tonal tweak to bring everything together in our photo. We go to the Layers panel, click the Adjustment Layer icon and choose Channel Mixer. Now we select the Red channel and set Red +200, Blue -50, Green -50. Then we select the Blue channel and set Blue +200, Red -50, Green -50. Lower layer opacity to 30%.

Quick tip

The Refine command is essential for improving the edge of complex selections. The key feature here is Border Width, which expands the search area along the edge in which the tool seeks out similar pixels to those already included. As such, it’s ideal when we need to select tricky edges like areas of hair, fur or foliage. We can also paint over tricky areas with the dedicated Adjustment Brush set to Matte, then fine-tune by using the Foreground and Background buttons to tell the command what should be included (foreground), or left out (background).

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The lead technique writer on Digital Camera Magazine (opens in new tab)PhotoPlus: The Canon Magazine (opens in new tab) and N-Photo: The Nikon Magazine (opens in new tab), James is a fantastic general practice photographer with an enviable array of skills across every genre of photography. 

Whether it's flash photography techniques like stroboscopic portraits, astrophotography projects like photographing the Northern Lights, or turning sound into art by making paint dance on a set of speakers, James' tutorials and projects are as creative as they are enjoyable. 

As the editor of Practical Photoshop magazine, he's also a wizard at the dark arts of Photoshop, Lightroom and Affinity, and is capable of some genuine black magic in the digital darkroom, making him one of the leading authorities on photo editing software and techniques.