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How to Create Masks of Transparent Elements in Photoshop

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Selections are an essential part of any photo editing workflow, but often, selections aren't as straight-forward as they might seem. In this tutorial we will explain how to make a selection of a glass that includes transparent elements. Let's get started!


Tutorial Assets

The following assets were used during the production of this tutorial.


Step 1

Selections are an essential part of the image editing process in Photoshop. The process of making a selection is easy but sometimes transparent areas can make the process a bit more complicated. For these types of project, the pen tool is not sufficient. To select areas with a variable level of transparency we need a tool or command which will let us manipulate the brightness information of the color channels of that image. Because we are not only interested in creating a simple cut-out, rather we are more interested in creating a mask, where we can store variable level of brightness information for defining that complex level of transparency. As a channel is just a grayscale image we can use that channel effectively to create a mask, because a mask also uses grayscale (pure white=100% opaque and pure black= 100% transparent) to store transparency information.


Step 2

One of the major advantages of having access to the separate channels in Photoshop is the ability to make selections. You can use individual channels to make different selections in the image. When you want to select a specific item in the image, use the color channels that provide the greatest contrast around the edges of that item. So let’s start the initial planning phase.


Step 3

This is the original image. Though this is a CMYK image, same process will work in case of an RGB image. Only difference will be in the Channels panel. Instead of four color channels and one composite channel, there will be three color channels and one composite channel in the RGB image. The objective of this tutorial is to remove the black portion but to keep the glass, water, bubbles and the reflection below the glass. So we can use it on any other background (Solid color or photo). For this tutorial we will use Apply Image command (Image > Apply Image).


Step 4

The Apply Image command lets you blend one image’s layer and channel with a layer and channel of the active image. But remember the pixel dimensions of the images must match for image names to appear in the Apply Image dialog box. But here we are not using two images. We are blending the black channel copy with the black channel copy itself. But the power of the Apply Image is hiding within the Target section. Here you can specify a blend mode or blending type which you want to use during the Apply Image blend.


Step 5

Open the file in Photoshop. Then in the Channels panel examine the channels for a channel with good contrast. Finding a channel with good contrast is essential for good selection.


Step 6

Here the black channel is showing good contrast between the glass and the background.


Step 7

Duplicate the black channel by dragging it over the ‘create new channel’ icon below the Channels Panel. You can also right click on the black channel and select duplicate channel.


Step 8

Then select the black channel copy and Image > Apply Image.


Step 9

First blend one time with Multiply mode to increase black and in this process convert from the background any area to black which is gray. But reduce the opacity (within the Target section) amount to 50% to create a blend which is not too strong. Otherwise we might remove some white areas, as they are not pure white.


Step 10

The Multiply blend mode looks at the color information in each channel and multiplies the base color by the blend color. The resultant color is always a darker color. Multiplying any color with black produces black. By using the Multiply blend mode we are removing any grey portion from the background.


Step 11

Then blend two times with Overlay blend to increase white. Now we can easily select the white area. Our goal here is to create an effective, fast and acceptable mask with this process. This time use 100% Opacity in the blending area.


Step 12

The Overlay blend mode multiplies or screens the colors, depending on the base color. The base color is not replaced, but mixed with the blend color to reflect the lightness or darkness of the original color. White areas become brighter and black areas become darker. By using the Overlay blend mode we are increasing the strength of the white portion as we want to keep the white portion but mask out the black portion in the final image.


Step 13

You can still tweak the black channel copy by using a brush and paint with white or black color. Paint with white to keep image areas and paint with black to remove or mask out portion. White denotes opaqueness and black denotes transparency within a channel.


Step 14

Load the black channel copy as a selection by either Command/Ctrl-click on the channel or click the first button below the channels panel, which is load channel as a selection.


Step 15

Then go to the Layers panel and duplicate the background layer by dragging it over the create new layer button below the layers panel. You can also right click on the background layer and select Duplicate Layer.


Step 16

Then target the new layer (Background copy) by left clicking on it once. Selection still active, click on mask icon below the Layers panel to create a mask.


Step 17

Now create a new blank layer below and fill it with either red or blue. Now check the quality of the mask. You will find that within the mask there are few grey areas.


Step 18

There are two processes to remove this unwanted grey area. Although first process described below will give you the best output, but still let’s explore both of them.


Step 19

Process 1: Change the blend mode of background copy layer to Lighten in order to remove grey area.


Step 20

Lighten blend mode looks at the color information in each channel and pixels darker than the blend colors are replaced, and pixels lighter than the blend color do not change. As a result dark grey pixels removed.


Step 21

Process 2: Command/Ctrl-click on the background copy mask thumbnail to load the mask as a selection. You can also load the selection from the black channel copy.


Step 22

Then click on the Adjustment layer icon below the Layers panel.


Step 23

This will create a new Levels Adjustment layer.


Step 24

Then in the levels dialogue box first drag the midtone input slider (middle one) and then the highlight input slider (right one) towards left to remove grey area or rather converts grey into white.


Step 25

After applying Lighten blend mode, if you check closely you will find that there are a few broken portions within the white area. You can use the Clone Stamp Tool to fix these areas.


Step 26

That’s it. You can use the same technique to select complex objects with variable level of transparency. Below is the before and after version.


Final Image

This is the final version.

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