Selecting objects with different levels of transparency occurs through the brightness information from the color channels of the image. We can create a mask for the photo, as it uses grayscale, as well as channels. In this case, the white color will be 100% opacity photos, and clean black – on the contrary.
In our example, you need to use separate channels to create different selections. Not much difference in CMYK or RGB, but it must be remembered that in the first case is 4 channel and the second 3.
So, the purpose of this lesson is to completely remove the dark area and keep the glass, its reflection, the water and bubbles. Thus, in the future it will be possible to use it on any other background or pictures.
Download the image from the glass, go to the channels panel and select from them the most striking. Try this method, it is possible just by clicking on the respective channel.
In the specific example we have the most striking is the channel Black . Copy it by dragging the icon create a new channel Create New Channel , or by clicking the context menu item Duplicate Channel.
Next go to the layers panel, go to programs Image – Apply and select Multiply.
Approximate opacity Opacity this item 50%. This will enhance the black color, and also converts any grey areas just background more black.
Now apply the same action, but instead Multiply set Overlay and the degree of opacity change to 100%. Thus we can easily select the white area. The purpose of this process is to create an efficient, fast and affordable mask for subsequent processing.
Go back to channel panel and load a selection of the black channel, just by clicking its thumbnail while holding the Ctrl key, or click the first button at the bottom of the channels palette, which will produce a similar effect with the selection.
In the layers panel, duplicate the main layer with Ctrl + J or selecting from menu Duplicate Layer.
Add a mask to the layer with the active selection, i.e. still selected channel, click on Add Vector mask at the bottom of the layers panel.
Then create a layer under just copied and fill it with any solid color such as blue.
There are two methods to remove unwanted grey areas. Consider both.
First – go to layer mask and set the blending mode to Lighten.
The blend mode reads the color information in each channel and the pixels which are darker than the blend color are replaced, and no lighter. In the dark gray pixels are removed.
Now consider the second method. Click on the thumbnail of the layer mask with a copy background, hold down Ctrl key to load the selection mask. Load the same selection from the copy of the black channel. Click the create new adjustment layer at the bottom of the layers palette.
Then at the bottom of the layers panel, select Create new fill or adjustment and choose Levels. The average move the slider to the left to adjust the midtones.