Sooner or later every photographer wants to learn how to remove backgrounds from images in Photoshop. Maybe they are trying to isolate an object to use in a composite. Or maybe they want to remove the sky to replace it with a more dramatic one. Whatever the reason, it is definitely a skill every advanced post processor should know.
Select the Subject
The first challenge is to select either the background to be removed or the subject to be isolated. There are several options to do this. The least eloquent of these is to use the Quick Select tool in Photoshop. If your subject is uniform in shape and coloring, this method will probably be sufficient.
However, if there are irregularities to the subject, other tools may be more appropriate. The Select – Subject menu option can work well providing the subject is well defined. If you shot on a Green Screen the Select – Color Range is probably your best option.
The most precise, and tedious, method is to use the Pen tool to draw the boundary of the subject to select.
Regardless of the method chosen, detail like wispy hair can be impossible to define without further refinement, which is where the Select – Select and Mask tool is used.
Select and mask
Refining the selection using this tool is a straightforward process. In the Select and Mask dialogue box, Set View Mode to View on Layers to clearly show the selected areas. In Edge Detection, set Radius to 4px and check the Smart Radius box. Now use the Refine Edge Brush Tool to work around the edges to remove, or OPT (or ALT on Windows) Refine Edge Brush Tool to add back in, pixels around the edges.
Tick the Decontaminate Colors and adjust the Amount slider to ensure none of the background color tint remains (this is especially important for green screen), and choose Output to New Layer with Layer Mask. The subject is now isolated with a clipping mask.
To remove the background, simply CMD-Click on the output layer, choose Select – Inverse from the menu bar, click on the background layer and either mask or delete the pixels.
Masking with Channel Pull
For trickier selections, using the alpha channel channels to pull selections for a mask can be the most eloquent solution if you have an advanced comfort level with Photoshop. Let’s use this image as an example and use channel pulling to remove the sky.
First, duplicate the background layer (to preserve the original) and work on the copy level. Open the Channels panel. Click through the RBG layers to find the one that gives you the most contrast between the subject and the background ( in our case the blue in the sky makes the blue channel the one to work with) – and duplicate that layer.
Create a Level adjustment and use the sliders to make the background pure white and the foreground as dark as possible without losing details.
Using Cmd-Click will select all of the white areas. Sometimes you will select some of the foreground area especially if it is the same color as the background. You can either use the Quick Selection Wand to remove those areas or see how we deal with that in a minute. Now enable the RBG channel and disable your Channel copy. Return to the Layers panel. Since we want to mask out the background (the area that is currently selected) and keep the foreground, let’s Select – Inverse to select the subject area, and then use the Add to Layer Mask icon at the bottom of the panel.
The mask now completely removes the sky background, but you may notice that’s some of the foreground (especially the blue areas) have been removed as well. Paint them back in by clicking on the mask, choosing the paintbrush with white in Overlay Mode on a hard brush and paint over the areas to bring it back in.