On1 Sky Swap AI Plug-in Review
On1 Sky Swap AI Plug-in Review
In this review, we’re looking at the new On1 Sky Swap AI plug-in for Photoshop. Although we don’t cover it in this article, I’ve also tested this plug-in with Affinity Photo, and it works great.
Before we look at some of the features of Sky Swap AI, I should say that I’m using the trial version of the software. I’ve decided not to purchase the plug-in as it’s not a feature I use much, and I already have it in On1 Photo RAW 2023. It works the same way in both products, but you can’t use On1 Photo RAW 2023 as a Photoshop plug-in.
Opening On1 Sky Swap AI Plug-in
When using the On1 Sky Swap AI plug-in in Photoshop, it’s always a good idea to start by duplicating the image layer you’re working on. You can do this by right clicking the image layer in the Layers Window and choosing the “Duplicate layer” option. Alternatively, you can click the layer in the Layers Window to select it, and then press Cmd + J on a Mac or Ctrl + J on a Windows PC.
Having created a duplicate image layer, you should convert this layer to a Smart Object. This allows the On1 Sky Swap AI plug-in to act as a Smart Filter, saving your settings as part of the layer. Then later, should you want to make any changes, you can reopen the layer in the plug-in, and it will have retained your adjustments.
To convert the image layer to a Smart Object, first click to select it in the Photoshop Layers Window. Then click the “Filter” menu at the top of the Photoshop interface and choose the “Convert for Smart Filters” option.
You can then launch the On1 Sky Swap AI plug-in from the Filter menu.
Examining the Sky Swap AI Mask
When the plug-in launches, it will analyse the image to identify the sky and produce a mask to select it. You will be able to see this mask at the top right of the filter controls as indicated in the following screenshot.
If you’re an existing On1 Photo RAW user, you will probably recognise this interface immediately. The Sky Swap AI plug-in is just a cutdown version of that software with a single filter.
Towards the top of the controls section, you can see a small thumbnail. This represents the mask that’s been produced by the software. When you click the thumbnail, the section expands to reveal a slightly larger version together with adjustment controls.
Identifying Selection Problems
The best way to examine the mask for problems is to click the View button. This then displays the mask in the main preview area as shown below.
Here you can see the mask with two problems indicated by the arrows. They are:
- A dark halo around the building.
- A bright area of road/pavement which has been selected as part of the sky.
To see how these problems affect the result, let’s choose a replacement sky for the image. First however click the View button a second time to return to viewing the image, rather than the mask.
Choosing a Replacement Sky
The On1 Sky Swap AI plug-in comes with over 200 high-quality skies that you can use. In addition, you can import your own skies, which you may have purchased or photographed yourself. You will find this option just below the mask controls as indicated below.
In the screenshot you can see four sections of controls indicated. These are:
- Icons and dropdown which can be used to choose the category of sky to use.
- The import button to import your own replacement skies.
- Category, which is the first of two dropdowns. Like the icons mentioned above, you can use this to select the category of sky to use.
- The second dropdown is a list of skies in the selected category, and which are displayed as a thumbnail list.
For this example, we will choose one of the skies from the Clouds category. When we then click the sky dropdown, we can move the mouse pointer over each thumbnail. This then displays a preview of the sky on the main image as shown below.
The sky in this example was deliberately chosen as it highlights the two problem areas in the mask. We can see the dark halo around the building allows us to see part of the original (lighter) sky. Then we see the sky in the bright area where light is reflecting off the road/pavement.
The chosen sky also highlights a common problem with all sky replacement software. That is, you need to select a sky that complements the lighting of the original image, or the results appear false.
In this example, the sky is much darker than the original image. What may not be immediately obvious, is that the On1 Sky Swap AI plug-in has attempted to change the lighting in the original image to match the sky. We will look at how it does this in a moment, but first we need to fix the problems in the mask.
Fixing Problems in the Sky Swap AI Mask
When I first began working with the On1 Sky Swap AI plug-in, I was tempted to fix the mask problems using the masking controls. As I soon learned, this wasn’t the best way. That’s because the controls of the filter are causing the problem.
Removing the Building Halo
As it turned out, the halo around the building is being caused by the Fade Edge slider and not the AI selection. You will find this control in the Position section, as indicated in the following screenshot.
When the Fade Edge slider is in the central default position, it creates a dark halo around the edge of the mask. When we move this to the right it increases this halo, but when we move it to the left it reduces it. If you move the slider all the way to the left, it causes the halo to invert so that we see a white halo spreading into the mask. This would cause the replacement sky to bleed into the building in this image.
The Shift Edge slider then allows us to fine tune the position of the edge of the mask. This produces very small shifts in the edge of the mask and is probably best used after the Fade Edge control.
Below are three versions of the mask at 100% magnification and using different Fade Edge settings.
The settings used in these examples are:
- +100 which is the maximum value for the slider.
- -100 which is the minimum value for the slider.
- -50 which seems to remove any halo around the sky.
Fixing the Reflection Problem
The other problem we need to fix is where there is a bright reflection on the road/pavement which is being mistaken for sky. To fix this, we will need to use the masking tools provided in the On1 Sky Swap AI plug-in. You can select these by viewing the mask as we did previously.
After clicking the mask thumbnail to select it, you will see the masking tools on the left of the screen and along the toolbar at the top. You can then choose the tool you want to use as shown in the following screenshot.
For this repair we’ve chosen the regular Masking Brush (top) from the “Mask” controls (left). Then in the toolbar at the top, the brush is set to “Paint out”. It’s then possible to paint over the white areas of the mask to remove them.
You can see the before and after version of the mask below.
The mask on the left is the original, showing unwanted white areas. The mask on the right shows the repair using the Masking Brush.
After repairing the mask, choose a suitable sky to use.
Addressing Lighting Problems
Having selected a replacement sky, we see a big improvement in the image. There is however another problem which can be seen in the screenshot below.
If you look at the bright area of pavement in the bottom left of the frame, you can see that it’s still very dark. This is being caused by the settings in the “Foreground” lighting section of the filter. This attempts to adjust the lighting of the original image to match the sky.
This lighting adjustment is applied to the entire original image. There is however a horizontal cut-off, which in this example is near to the bottom of the image. You can see where the image transitions between a bright reflection on the road at the bottom left to being dull grey above this. The adjustment works like a Neutral Density filter that you place over the end of the camera lens. The cut-off point is then controlled by the “Distance” slider which moves it up or down.
Whilst this might work well for landscape images, it isn’t working in this example. It would have been much better if the software had a second mask here. We could then have used that to control where the lighting effect is visible.
Despite this, it’s possible to correct the lighting to avoid the problem. You can do this in one of two ways which are demonstrated in the following video. The video also shows the features explained so far, together with a few others. You will also see the On1 Sky Swap AI plug-in used with two more sample images.
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Review Thoughts For The On1 Sky Swap AI Plug-in
After using the On1 Sky Swap AI plug-in for a couple of weeks, I have some observations.
Generally, I like the software and find it works well with some images. The quality of the results is however mixed. Ultimately, the software is let down a little by the AI selection which needs to improve.
The filter includes several controls which are useful in refining the results. You do though need to take time to adjust the mask. A good mask will allow you to produce some excellent sky replacement images. What the plug-in doesn’t do, is automate everything.
If you’re considering this plug-in, I recommend downloading and experimenting with the trial version first. If you later decide to make a purchase, my On1 discount code does work. Please apply the code LENSCRAFT20 at the checkout to receive the discount.
Now, if you’re already a Photoshop CC subscriber, you can access the Photoshop sky replacement feature. This is another AI tool and an alternative to the On1 Sky Swap AI plug-in. If you want to know how to use that, read this tutorial next.
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