Based on channel mask (1)

In the previous exercise, we have seen how we can use “Color Range” to make a mask. However, when we want to work on something more specific, such as the hair of this young lady, we can use a mask based on a Channel.
In this example I have the picture of the young lady with the photo on the right as the background.

To begin, we open the “Channel” Palette.
We compare the various Channels, Red, Green and Blue.
We watch for the channel that provides the most contrast.
In this case, the Red Channel.
We make a copy of the channel by dragging the channel to the “Create New Channel” button at the bottom of the “Channel” palette.

We give our new channel a more appropriate name, eg “my mask.”
In the next step we increase the contrast of our new channel.
So first select the new channel, “my mask” and click “Image” – “Adjustments” – “Levels” .. in the menu bar.
This will open the “Levels” dialog.

I am going to increase the black value (20) and lower the white value (120).
These values are vary from photo to photo, it is possible that these values are ??above or below the values you need. Enter values ??in here so that you get the most contrast between the white and black level.
Click OK when you are satisfied.

In the next step we are going to eliminate gray, we do not need it in our channel.
Should we have done this in the previous step, in the Levels dialog box, then there would not be much left of the fine hairs.

We are here to make a mask, so everything we want to show must be white or gray value and everything we do not want to show should be black. In other words, her eyes, nose, mouth, etc. must be white.
First we need a little work, we use the “Dodge” tool to eliminate the gray hair on the edge.
Select the “Dodge” tool and click and drag over the hairs to make this white.
This will be time consuming, but this is the only way to get good result.

Once we are done with the “Dodge” tool, it is a bit faster to make the rest of her face white.
For this, select the “Lasso” tool in the toolbox and drag completely around her face so that everything is selected.

Normally we would be able to click the Delete button on our keyboard to delete all of this, but our background color will become black and we do not want that, we want white.
The default values ??of the foreground color and background color, namely white and black, in an Alpha Channel.
So we click the Alt + Backspace key on our keyboards and this gives the white background that we wish (see next lesson).

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