How to replace a sky with Photoshop.
Compositing gives photographers the magical power to change the weather. Most people crave a sunny sky but for conceptual and landscape photographers the more colour and cloud in the sky the better. We go to so much effort to make a scene beautiful and interesting and are often let down by those bright, washed out skies. This is why photographers like to be up at the crack of dawn capturing sunrises. It’s also why photographers who don’t use Photoshop buy expensive filters, why photographers who do use Photoshop take two exposures—one exposing for the land and one exposing for the sky—and blends them together. And then there’s the third camp who are perfectly comfortable messing with reality and swap their skies for entirely different ones. This is the sleeper-inners method so stick with me to learn how to replace a sky if you’re not a morning person.
If all horizons were straight and not covered by mountains and trees then replacing a sky would be a breeze but things just aren’t that simple. Because of this there’s more than one way to replace a sky in Photoshop and it can take some experimenting to find the one that works best for your image.
Choosing your new sky
In last week’s lesson I talked about collecting photos of clouds and skies for the purpose of swapping them into new scenes. So when looking for a sky image there’s a few things to keep in mind:
- You’ll want to find a sky lit the same way as your foreground. If your subject is side lit from the left you should look for skies where the sun is also on the left. You can always flip your sky image to get the lighting in the right spot.
- To save on colour work it also helps if your sky is a similar colour to the foreground. A dark overcast sky probably won’t work with a sunrise lit landscape.
- If you want your image to look realistic try and line up the horizon lines in both images or the sky may look unnatural. Skies look different near the horizon than they do in the middle of the sky. If you’re a conceptual photographer you have some leeway with this because you’re building an ‘otherworldy’ scene anyway.
- To save on work make sure your sky image is free from distractions like light poles or power lines, though you can always clone these out if there’s a sky you particularly like. Or you can hide them by dragging your sky layer lower behind your subject image.
- Keep in mind that skies are pretty flexible and can usually be stretched and resized a fair bit before they start to look weird.
How to replace a sky in Photoshop
I personally like to experiment with a few sky options rather than limiting myself to one. So in Lightroom highlight all your chosen skies and go to Photo->Edit In->Open as Layers in Photoshop and then one by one, use the move tool (V) to drag each sky up to the document tab of the foreground image and then down onto the canvas. Lower the opacity of your sky image using the Opacity setting in your layers palette and move your sky into place. Edit->Transform->Flip Horizontal if you think the sky will work better flipped. If you want to scale or stretch your sky image press Ctrl/Cmd T and drag the corners of the bounding box to resize. Hold down shift if you want to resize with the same proportions.
In no particular order here’s all the different methods I know of for adding a new sky.
Method one for replacing a sky – selection tools: Color Range
This method works best if your original sky is primarily one flat colour. Drag your sky layer below your subject layer. With the subject layer highlighted go to Select->Color Range. I prefer to use ‘Sampled Colors’ and then use the eyedropper to sample the original sky’s colour but you can also try choosing ‘Blues’ in the dropdown menu. In your preview box you can see what will be selected (areas of white) and what won’t be selected (areas of black). Play around with your fuzziness slider to refine the selection and use the + and – eyedropper tools to add and remove from your selection. Click OK when you’re happy. If the selection has missed any bits you can choose the lasso tool and holding down Shift draw around any bits of the sky you want to get rid of. Press the add layer mask button which might apply the new sky to your foreground. Obviously this is not what you want! So press Ctrl/Cmd i to swap your mask’s colours. And there you have it—a new sky!
Method two for replacing a sky – selection tools: Magic Wand
I find the magic wand tool a little more flexible than Color Range as you can use it on skies that vary in colour. Grab your magic wand tool (W) and click on your original sky. Play around with the tolerance settings in your options bar if it’s not selecting enough or too much. Shift click any others areas you wish to add to the selection and Alt/Opt click any you wish to remove. Your aim here is to make sure the horizon line is properly selected. If the magic wand tool has also selected some of your foreground you can activate the lasso tool (l), hold down Alt/Opt and just draw around an areas you don’t want included in the selection to remove them. Then, as above, hit your add layer mask button and invert the selection if necessary.
If you find the magic wand tool has given you jagged edges you can click on your mask and go to Select->Refine Edge. Play around with the sliders, particularly ‘Smooth’ and ‘Feather’ until the edges look better.
With these first two methods if you find you’re getting haloing around leaves on trees I recommend watching Glyn Dewis’s video for advanced tips on how to fix this.
Method three for replacing a sky – Blend If
‘Blend If’ is a cool little feature that’s useful for many things. It doesn’t really matter what order your layers are in but for this example I’ve placed the sky layer below the subject layer. Now with your subject layer selected, double click it to open the ‘Layer Style’ dialogue box. Make sure Blending Options: Default is selected on the left hand side and down the bottom you will see two sliders. Your aim here is to ‘Blend if the underlying layer is darker’—so the washed out sky of your subject layer will disappear in the areas where your replacement sky layer is darker (this works best if your original sky is very pale and your new sky is darker). It’s trickier than it sounds. Alt click the left hand triangle on the ‘Underlying Layer’ slider and drag it to the right until your new sky begins to show up. Refine this by dragging the second half of your black slider to the right. Play around until you like how it looks. If this method messes with your foreground, place a layer mask on the new sky layer and brush it away from where it’s not wanted.
* This method left horrible white fringing around my subject layer that I couldn’t get rid of so if you’re finding this too I’d try another method.
Method four for replacing a sky – blend modes
For this method I’d drag your sky layer above your subject layer. With the move tool selected (V) press Shift and + or – to cycle through your blend modes which can be found in the layer’s palette under the drop down menu that says ‘Normal’. If your sky is close to pure white you might find ‘Multiply’ works best. When you find one you like, add a white layer mask to your top layer and with this mask selected choose a big soft brush set to around 50% opacity and brush the new sky away from your subject and foreground. You may have to switch between black and white brushes to refine the mask until you’re happy. Be sure to erase the seam of the new sky image at 100% to get rid of any harsh lines.
Method five for replacing a sky – gradient
This method is my favourite for replacing skies although if you’re looking for a very exact horizon line you won’t find it here. I like this method because it brings some of the sky over your image which adds atmosphere. It was particularly great for my image this week to mask out the distracting trees in the background (see my final image for the result!) Place your sky layer above your foreground layer. Add a mask to the sky layer and grab the gradient tool (G). In your options bar at the top, click on the drop down arrow next to the gradient bar and select the third option along the top which is black->white. Also make sure that the linear gradient is selected (the first box to the right of the gradient bar). With the sky’s mask selected drag your gradient tool from the bottom of your image towards the top. This creates a smooth gradient mask that makes your new sky fully visible at the top, tapering off to reveal the foreground underneath. If you didn’t get the gradient quite right keep redrawing it until you’re happy. Vary the position where you start drawing the gradient and the length of the gradient you draw. With your mask still selected you may then have to use a soft brush tool loaded with black to erase the effect fully from your subject.
If you’re experimenting with different skies and you’re working with one of the above methods that uses a mask you can Alt-click and drag your mask from one layer to another without having to create it again each time. When your new sky is in place I’d suggest playing around with the colours of the overall image (a selective colour adjustment layer is my go-to method) to make your sky and your foreground look like they belong together. A texture or noise layer may also help.
About ‘Time Flies’
I chose a location to shoot this image which put the girl on a hill so I could shoot from below and see the sky behind. But I just wasn’t able to get back to the location to photograph it. Instead I cheated and shot myself in my backyard against a white sheet with the camera on the ground pointing up. So I’ve actually already replaced the background in this image once by painting a white mask around her. I then flattened her layer with a white solid colour layer and the lavender image for the purpose of this week’s example, however sometimes cutting out your person and sticking them on a new background might be the best (although not the easiest) solution to replace a sky. The lavender was photographed at Maleny Botanic Gardens, while the clouds were shot from my front yard. Three textures were used.
Let me know which method works best for you and if you know of any others please add them to the comments!