Adobe added AI-powered sky replacement to Photoshop in late 2020. You can quickly and easily replace the sky in any photo with a different one. It’s a pretty neat feature, but it has a few quirks. Here’s how to use it to make a believable photo.
This tutorial is kind of split in two. First, we’ll cover the actual mechanics of the tool, and then we’ll look at some of the problems you might encounter when trying to create believable images. Sky-swapping is nothing new for photographers, but the automated Photoshop tool makes it a lot more accessible for beginners and faster for experts. Let’s dig in!
How to Use Photoshop’s Sky Replacement Tool
To get started, open the photo you want to edit in Photoshop. We’re using the shot above of a lighthouse. The sky in the image looks okay, but it could use some punching up.
If you click Edit > Sky Replacement, you’re in the Sky Replacement tool. Most of the heavy lifting is done by Adobe’s AI/machine-learning algorithms (called Sensei), but there are still a few options to break down here.
To select a sky, just click the sky preview image, and then click any of the options. The tool ships with about 25 default skies in three categories: “Blue Skies,” “Spectacular,” and “Sunsets”.
They’re all pretty decent. However, keep in mind they’re the default skies built into Photoshop, so they’re going to be very popular.
A better option is to go with your own sky. To do that, click “Create New Sky” at the bottom right. Navigate to any photo you’ve taken (or found on a site like Unsplash) that has a dramatic sky, and then click “Open.” The sky you select will immediately appear in your image.
Tweaking the Sky Replacement
The rest of the options in the Sky Replacement tool are for tweaking things to make the overall image look natural. You’ll see the following tools on the left:
- Sky Move tool (keyboard shortcut V): This works just like the normal move tool. You can click and drag the sky to reposition it in your photo. In the images above, the sky I selected added a mysterious island to the background, so I’m going to use the move tool to get rid of it.
- Sky Brush tool (keyboard shortcut B): This one’s a bit different from the regular brush tool. It allows you to paint over any area and tell Photoshop you want to add more of the new sky to the image. You can also press and hold Alt (Option on a Mac) and paint to tell Photoshop to remove some of the new sky. You don’t have fine control, but it’s handy for correcting any small errors the AI makes.
- Hand (keyboard shortcut H) and Zoom tools (keyboard shortcut Z): These are like the regular tools. You can click and drag with the Hand tool to move around your image or click the Zoom tool to zoom in. Press and hold Alt or Option, and then click to zoom out.
There are additional sliders, checkboxes, and drop-down menus, including:
- “Shift Edge”: Moves the border between the new sky and the foreground. Negative numbers add more foreground, while positive numbers add more sky.
- “Fade Edge”: Blurs and feathers the border between the new sky and foreground. Use a higher number when the transition is blurrier, and a lower number when it’s more delineated.
- “Sky Adjustments”: The “Brightness” slider darkens or lightens the new sky, while the “Temperature” slider alters its white balance. The “Scale” slider changes the size of the background image and the “Flip” checkbox flips it around its horizontal axis.
- “Foreground Adjustments”: “Lighting Mode” gives you a choice between “Multiply” (the sky will darken the foreground where they overlap) and “Screen” (the sky lightens the foreground where they overlap). “Lighting Adjustment” controls the strength of the brightening or darkening. “Color Adjustment” controls the strength of Photoshop’s AI-powered recoloring of the foreground based on the new sky.
- “Output”: Here, you can “Output to New Layers” (the better choice), which creates separate layers for all the effects. If you select “Output to Duplicate Layer,” it merges everything into a single flat layer.
- “Preview”: Selecting this checkbox toggles the image preview on or off. It’s great for seeing how your new sky compares to the old one.
The only way to really get a feel for the sliders and options is to play around with them and see how they affect the sky in your image. When you’re happy with everything, just click “OK.”
The Pitfalls of Sky Replacements
From a technical perspective, sky replacement in Photoshop is now really easy. You just open an image, play with a few sliders, and boom! New sky.
Below is the before and after versions of our image.
Even when you zoom in super close, you’ll see Photoshop does a really good job. In our image below, the glass through the center of the lighthouse looks a little off, and some wires and one of the birds has vanished, but we’re looking for problems. You can mostly look at the edited image without horror.
The same can’t be said, for every image, however. Below is another shot of the same lighthouse. Can you spot the issue?
How about this shot of a different lighthouse? The problem here is a bit easier to spot.
How about the image below? It’s actually from Adobe, and it’s got some serious flaws.
Did you spot them all? Here’s what we found:
- In the first image, the old sky is still reflected in the smooth water.
- In the second image, the sky is just way too over the top for the foreground. No amount of machine learning can fix that.
- In the third image, the sun’s position has shifted much lower and to the left. This means the dramatic lighting on the surfer and his board is at odds with the direction of light.
Here’s an even worse example of that last issue.
The colors actually blend pretty well here, despite how dramatic the sky is. However, the sun is clearly in the left of the frame, while the shadows and highlights on the woman and her dog are from a sun that’s rising somewhere on the right.
It’s awesome that the Sky Replacement tool is so quick and easy to use. However, that also means you can use it without giving it much thought. There are a lot of potential pitfalls that come with replacing a huge chunk of an image—especially if you want it to look realistic.
And realism is important. Most people will detect that something isn’t quite right with an image when the direction of light is wrong or the colors don’t match. They might not be able to explain exactly why things are off, but they’ll know.
How to Get Sky Replacement Right
The golden rule of sky replacement is the more similar the sky you swap in is to the one you’re swapping out, the better. Instead of looking for a ridiculously dramatic sky, try to find something that looks like the one in the image, but better.
The two biggest things to look for are light direction and color. If the light direction is different, there’s nothing you can do in Photoshop to make that right. No amount of playing with sliders can change the direction of the shadows in the foreground. So, start with a sky that has a similar light direction, and use the Move tool, and the Scale and Flip options to align it.
Colors are a bit easier to fix because, if you’ve got Photoshop skills, you can adjust them quite a lot. Still, there’s a limit. If you’ve got a very contrasty, saturated foreground, go with a contrasty, saturated, dramatic sky. If the foreground is a bit more muted, a sky that’s likewise understated is going to work better.
Also, light is different colors at different times of the day. If your image is from the blue hours of predawn, a golden sunset is going to just look wrong. The more similar the sky and foreground colors are at the start, the better the finished image will look.
The best thing about Photoshop’s Sky Replacement tool is, as long as you select “Output to New Layers,” all the automated edits are added as editable layers and masks. This means you can go in and edit things with manual tools afterward and use the full power of Photoshop on your image.
Like pretty much everything, the only way to get good at photography and Photoshop is practice. It’s cool that replacing a sky in Photoshop is no longer a technical challenge, but a creative one. So, be sure to try different things. Push your images too far and, when it all looks wrong, try to figure out why.