TOOLS & TIPS

A Comprehensive Introduction to Photoshop Selection Techniques

by AHMAD

Have you ever had difficulties making selections and thought there was a better way? Let's review both quick solutions, and on the other side, comprehensive and details techniques for making selections. Each approach has it's place in your workflow. The more methods you know how to use, the faster and more effectively you'll move in Photoshop.

Selection in Photoshop

Photoshop selects pixels based one of the three properties, as shown in the image below:

1. Chroma: is the color of the pixel. Color of a pixel is the level of RGB values and color based select tools like the
   Magic Wand. Select by color uses the RGB% as a criteria to group pixels based on the set tolerance values.
2. Luma: is a selection based on Illumination levels. Illumination levels are whiteness of the image, which is nothing but higher values for all the three R, G and B channels. Photoshop doesn't have a native interface for a Luma based selection, but many existing tools can be hacked to get a similar result.
3. Masks: are based on spatial position. Pixels are selected and discarded or masked by a parallel layer bound to corresponding image layer. Masks are grayscale and brightness of the mask is called an Alpha level, which is the degree of opaqueness of the corresponding layer pixel. It's also called the Transparency/Opacity channel as in RGBA etc.

A Note on Masks

In this article, words like Masks and Alpha will be used interchangeably. The process of transferring images to layer masks will be shown once and then used repeatedly without explicitly mentioning thereafter.

Step 1

Open a new image that you want to use as a mask. Double-click the background layer and create a new layer, which is "Layer 0." Make a new layer, which is "Layer 1," on top of it and fill with a uniform color, then hide "Layer 1."

Step 2

Go to "Layer 0" and click Select > Select All (Command + A) to select all pixels. Next, click Edit > Copy (Command + C) to copy all pixels to the clipboard.

Step 3

Go to "Layer 1" and create an empty Layer Mask. Initially an all transparent Layer Mask will be created. Alt-click the layer mask to see it in the canvas.

Step 4

With the Layer Mask visible, paste onto the canvas by clicking Edit > Paste (Command + V). A grayscale version of the copied image will be pasted in as the layer mask.

Step 5

Click on the fill layer thumbnail (not mask) to see the result. Any image can be applied as a Layer Mask to another layer. The opacity of the layer will be controlled by grayscale level of the mask.