Fix a lacklustre sky

James Paterson enhances a disappointing sky and demonstrates how to composite photos together with fundamental selection and masking skills

Add vibrant skies to images in Affinity

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.

Select the land

Open sky_before 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 and sea 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 ] and [ as you paint.

Drop in a sky

Set Output: Mask and hit Apply. Open the sky image, 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.

Perfect the mask

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).

Refine the edge

Click the Refine button at the top. Set Border Width to about 2% to control the area of refinement along the edge. Using the Adjustment Brush within the command, paint over any areas like the edges of the lighthouse here to direct the command to parts of the edge that need that little bit more refinement.

Improve the selection

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.

Tonal tweak

Finally, we’ll add a tonal tweak to bring everything together. Go to the Layers panel, click the Adjustment Layer icon and choose Channel Mixer. Select the Red channel and set Red +200, Blue -50, Green -50. Then select the Blue channel and set Blue +200, Red -50, Green -50. Lower layer opacity to 30%.