Quicklinks to all course lessons: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Lesson 3 sections: 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-JFF 3-IDEA
Lesson 3 sections: 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-JFF 3-IDEA
A03-05: Saving selections as alpha channels
Objective:
- Learn how to make a complex alpha channel mask from one of the color channels. Then see if you can do it yourself!
Learn:
As you've already learned, channels in Photoshop are gray-scale images that store different types of information. Color information channels are created automatically when you open a new image. The image's color mode determines the number of color channels created. RGB images have a channel for each color (red, green, blue), plus a composite channel used for editing the image (where all the color channels combine to form your color image). CMYK images have four color channels, plus a composite channel.
Alpha channels store selections as gray-scale images. You can add alpha channels to create and store masks, which let you manipulate or protect parts of an image. An image can have up to 56 channels. All new channels have the same dimensions and number of pixels as the original image.
When you spend a good deal of time selecting part of an image, wouldn't be nice to store that selection so you could always bring it back later on? Well, you can, by creating an Alpha Channel. OK, prepare to be amazed! Watch the videos below...
As you've already learned, channels in Photoshop are gray-scale images that store different types of information. Color information channels are created automatically when you open a new image. The image's color mode determines the number of color channels created. RGB images have a channel for each color (red, green, blue), plus a composite channel used for editing the image (where all the color channels combine to form your color image). CMYK images have four color channels, plus a composite channel.
Alpha channels store selections as gray-scale images. You can add alpha channels to create and store masks, which let you manipulate or protect parts of an image. An image can have up to 56 channels. All new channels have the same dimensions and number of pixels as the original image.
When you spend a good deal of time selecting part of an image, wouldn't be nice to store that selection so you could always bring it back later on? Well, you can, by creating an Alpha Channel. OK, prepare to be amazed! Watch the videos below...
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Apply: A03-05 Exercise. The Challenge!
Take this image of a tree, and mask the sky out using an alpha channel mask, as described in the videos above. Then add a different sky. Test yourself, but this doesn't need to be submitted. Here is a link to several sky images you could use! If you choose to use this as one of your three required exercise files, save your Photoshop file as A03-05_Your_Name.PSD. |
Original photo by gypsyugal from Pexels.com. Click image to download.
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After adding a different sky in the background, and adjusting colors of the foreground with a selective color adjustment layer.
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When Adobe released Photoshop CC 2021, they added a new feature in the edit menu - Sky replacement. It automatically does what these videos were showing you how to do with alpha channels. It's important that you understand how alpha channels work, so practice doing the tree selection that way. Knowing that skill will be important for selecting other complicated selections besides skies. Below are two good tutorials on using the sky replacement feature in Photoshop.
Video: Testing the NEW Sky Replacement Tool in Photoshop!
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Video: Photoshop 2021 Sky Replacement. Advanced tutorial.
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