Photo retouching is covering many topics, but one of the most used or requested is image background change.
There are challenges when the foreground objects have a too complicated structure. Hence, it is not possible or extremely time-consuming to use traditional selection tools like a lasso, quick selection tool, or magic wand, or even a quick mask.
Let’s go through the workflow, where we will try to change the sky background.
Contents
Image analysis before Photo retouching
Let’s have a look at the image and analyze what method should we use for selection. As we can see, there is a leaf in the foreground with a lot of holes. So it is not possible to use traditional selection tools. In this case, we will use the channel selection method.
Camera RAW Image preview
As we are opening the RAW image in photoshop, the default app that will open the image in the first step will be Camera RAW. In my case, I use Adobe Bridge for browsing and selecting the image for editing.
But you can use Adobe Lightroom or even just the file browser for the primary image selection process. This should be a standard process before any photo retouching process.
Fringing
So after opening the image in Camera RAW, let’s zoom in and check the details. As you can see, there is a fringing problem. Fringing appears on the edges between bright and dark parts of the image and has a specific color. In most cases, there is Purple or Green fringing. Defringing is a widely appearing problem to be covered by photo retouching.
So let’s go to the Lens Correction tab. First of all, let’s tick the Chromatic Aberration checkbox. You can see immediately the fringing disappears. In some cases, it is not 100% removed. In such cases, we go to another tab named Manual. It is a more advanced mode, where we can, even more, control fringe removal.
Here we have two main options available: the purple amount and the Green amount. Here we can define precisely the color tone of the fringing color to be removed. You can do it by moving the color tone sliders until you determine the dominant problematic fringing color on the image edges.
After that, move, for example, Purple amount to control the purple color or subtones of this color removal.
If necessary and you also discover green fringing let you use the same process for green fringing removal.
Selection using channels
The next step will be to separate the foreground from the background to enable to change of the sky with the new one. As we already mentioned, we cannot use standard selection tools and methods because the foreground is too complicated. So we will make the selection using the channels.
Let check which channel has the best contrast, and as you see, the blue channel will be our choice. Let us make a copy of the blue channel.
Always make a copy of any channel you want to use or edit to avoid destructive changes to the whole image.
With the new copy of the blue channel selected go to Image->Adjustments->Levels. Now move the sliders to increase the contrast. Be careful and don’t overdo it. In this particular case, I used the middle grey slider, and by moving it to the right side, I achieved more contrast between the leaf (foreground) and the background.
Keep in mind our goal is to make the black and white mask, and if there are any transparency areas, the mask should also contain grey parts.
Our next step will be to improve the contrast of the channel or better to say mask. We will use a brush tool with specific settings.
Let’s select a soft brush with a decent low value of Flow. I like to prefer to use Flow setting as you can paint the same part of the image, and the painting will build on each brush painting movement.
Now set the black or white foreground color depending on what you need to enhance. The critical point here is to select the Mode to Overlay.
New Background
Now choose the new background you would like to have in the final image. I use the Pexels extension for Adobe Photoshop.
This is an excellent free image resource for compositing or photo retouching. After logging in, you can choose a new background image. In my case, I look for a blue sky image to be my new background.
When you find it, just click on the image and it will be automatically inserted into your photoshop file as a new layer.
Photo retouching by masking the old background
The final step of the whole photo retouching - exchanging the background - will be to mask out the old background. So go to the channels and Ctrl+Click (on Windows) or Cmd + Click (on Mac) you will load the selection of the white part of the channel.
With the loaded selection unselect the copy of the blue channel, we just edited and then select the RGB channel. Then switch to the Layers and click on the new background layer - new sky image from the Pexels.
Now click the mask button on the bottom of the Layer panel.
Your new background should be masked in.
The next step now will be to fine-tune the mask to achieve a realistic view and compositing. This is an essential point in photo retouching - always fine-tune the final composite with the new background loaded and masked.
Conclusion
As you can see in this example, we demonstrated how is channel selection method useful in case of a complicated object selection. It used to be applied in case of selecting hair, for example.
This could be even more challenging, especially if the hair is on not clean one colored background.
Changing the background is the most common issue when speaking about photo retouching. So it could be quite simple but also a very challenging issue
