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Boundary Selections


Staff member
What is a boundary? A boundary is a limit of an area or a sphere of activity. I have mentioned the concept of using Boundary Selections, so now I need to explain.

Let's start by understanding the idea. In airbrushing, for this example, you might use something like masking tape to make a mask. A mask in airbrushing was used primarily to keep any paint from getting on the support where the tape was applied.

Screen Shot 2017-11-21 at 9.44.36 AM.png

Paint on tape....
Screen Shot 2017-11-21 at 9.44.53 AM.png

Tape removed....
Screen Shot 2017-11-21 at 9.45.09 AM.png

Masking in Photoshop has a different meaning so I needed to use another term.............I chose Boundary Selections.

Let's say we have made a template of the masking tape using the Pen Tool set to path. Then we save the path, convert the path to a selection, and fill the selection with black and we call it "Tape Template 1".
We now have a template for a given object (the tape) that we can use as a Boundary Selection.
Screen Shot 2017-11-21 at 10.56.26 AM.png

We can now turn off or deactivate the "Tape Template 1" and place it in a group.
We can, at any time return to the template and use it to make a selection by Cmd/Cntrl + clicking the templates thumbnail.

Using that (boundary) selection, we can paint inside the selection...
Screen Shot 2017-11-21 at 9.48.32 AM.png

...or by reversing/invering the (boundary) selection (note the marching ants on the outer edge of the canvas) we can paint outside the original selection (which technically is still inside the selection..........but let's try to avoid confusion).
Screen Shot 2017-11-21 at 11.05.13 AM.png

We could also use the (boundary) selection to create a layer mask to accomplish the same thing!

This layer mask......
Screen Shot 2017-11-21 at 11.12.16 AM.png

.....produces this.
Screen Shot 2017-11-21 at 11.11.19 AM.png

And this layer mask...........
Screen Shot 2017-11-21 at 11.13.59 AM.png

.....produces this.
Screen Shot 2017-11-21 at 11.14.08 AM.png

It's all in knowing and understanding the differences in how traditional airbrushing masking (tape) techniques translate to Photoshop.


Staff member
Ok. I want to add that I'm not claiming that using selections as boundaries is my idea................it's been used since Photoshop was invented. I just adopted the term "boundary selection" instead of selection or mask to avoid confusion and to simplify the understanding. A boundary selection is still just a plain old selection.

Let's put the idea of the boundary selection to practice.

Here is my practice image.
Screen Shot 2019-05-06 at 5.36.37 PM.png

Let's create a selection of the curb. I used the Pen Tool.
I can save the selection or save it on it's own layer as a template (turned off).

Here is the effective boundary selection of the curb.
NOTE: I 'm using Quick mask mode to demonstrate otherwise, this would be a marching ant selection.
I can only work within the constraints of the boundary selection.......
Screen Shot 2019-05-06 at 5.34.58 PM.png

Here I have completed my work constrained inside the boundary selection.
Screen Shot 2019-05-06 at 5.35.20 PM.png

Now let's invert that same selection so that I can work on the outside of the original boundary selection. (Technically, we are still inside the selection)
NOTE: Had we been using a marching ant selection, the marching ants would appear on the curb and the outer edge of the canvas.
By using the same selection and not creating a new one, I utilize the exact same lines of the boundary selection for the outside thus eliminating bleed over.
Screen Shot 2019-05-06 at 5.44.27 PM.png

Here is the completed work on the outside of the boundary selection.
Screen Shot 2019-05-06 at 5.46.16 PM.png

So, in conclusion...........I have used a selection to create a boundary or a limited controlled area with specific boundaries or boundary selection, to control the line of delineation between the curb and the grass and the curb and the sidewalk.


Staff member
Let's look at another use of setting boundaries with a selection.................Boundary Selection.

Let's remove this jeep. I want to preserve the sidewalk (at bottom) and the tree trunk.
Screen Shot 2019-05-07 at 10.35.43 AM.png

I use the Pen Tool to outline the boundary I wish to keep.
Screen Shot 2019-05-07 at 10.17.34 AM.png

I convert the path to a selection with a slight feathering to avoid hard edges which I will save on it's own layer as a template...........for future use if needed.
Screen Shot 2019-05-07 at 10.19.05 AM.png

I make sure the boundary selection is inverted (marching ants on tree, sidewalk, and outer edge of canvas) and I begin cloning out the jeep.
Screen Shot 2019-05-07 at 10.27.14 AM.png

The other side....
Screen Shot 2019-05-07 at 10.32.19 AM.png

Jeep removed. Some minor clean up and we can move on to the next.
Screen Shot 2019-05-07 at 10.46.42 AM.png

The layers panel.
Screen Shot 2019-05-07 at 10.33.53 AM.png