Quicklinks to all course lessons: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Lesson 2 sections: 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-JFF 2-IDEA
Lesson 2 sections: 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-JFF 2-IDEA
A02-03: Introducing Channels and Alpha Channels
Objectives:
- Understand how channels function within Photoshop
- Understand what alpha channels are
- Use a channel to create an alpha channel, and then use it as a mask to fix a color and luminosity problem in a photo.
Learn:
Understand how channels function within Photoshop
Now its time to open the hood and see the engine that drives Photoshop - channels. Photoshop uses channels to work with color and value in an image. Let's look at this photo's channels. Click each image below to see a larger view...
Understand how channels function within Photoshop
Now its time to open the hood and see the engine that drives Photoshop - channels. Photoshop uses channels to work with color and value in an image. Let's look at this photo's channels. Click each image below to see a larger view...
The channels palette.
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The red channel.
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The green channel.
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The blue channel.
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In this RGB color photo, each of these channels control the amount of red, green, or blue that shows in an image. Notice that the red channel is the lightest - indicating a large amount of red in the face. Although I strongly discourage you from playing directly with the color channels, I'm going to do it anyway to help you understand what's going on under Photoshop's "hood." Below left, is that image that is suffering a color balance issue! Let's see how manipulating channels can fix that. Watch the video below right.
This photo has a color balance problem. It is too blue! You can click on this image to enlarge, copy, and load it into Photoshop.
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Video: What's happening "under the hood" when you correct color with levels. (2:23)
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RGB images have three color channels (red, green, blue). CMYK images have four (cyan, magenta, yellow, black). Greyscale images have only one channel (grey).
As you learn more about channels during this course, you will see how powerful they are when it comes to making selections. That brings us to the next topic - Alpha Channels.
Understand what alpha channels are
Photoshop can have more channels than just the color channels. These extra channels are called alpha channels. A Photoshop file can have up to 56 channels. Alpha channels are saved selections. Alpha channels are created anytime you create a mask on a layer, use quickmask, or save a selection of marching ants. Alpha channels get saved when you save a Photoshop document. So, later on, when you call up that file again, you can go the SELECT menu and load the selection. Photoshop pulls that selection from the alpha channel. Another way you can load the selection is to go directly to the channels palette and Command-Click (CTRL-Click) on the alpha channel's thumbnail image.
As you learn more about channels during this course, you will see how powerful they are when it comes to making selections. That brings us to the next topic - Alpha Channels.
Understand what alpha channels are
Photoshop can have more channels than just the color channels. These extra channels are called alpha channels. A Photoshop file can have up to 56 channels. Alpha channels are saved selections. Alpha channels are created anytime you create a mask on a layer, use quickmask, or save a selection of marching ants. Alpha channels get saved when you save a Photoshop document. So, later on, when you call up that file again, you can go the SELECT menu and load the selection. Photoshop pulls that selection from the alpha channel. Another way you can load the selection is to go directly to the channels palette and Command-Click (CTRL-Click) on the alpha channel's thumbnail image.
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Use a channel to create an alpha channel, and then use it as a mask to fix a color and luminosity problem in a photo.
So, let's show you one more way to remove the red from the image we've worked on - using channels this time. Please watch the video, "Photoshop CC: Color Correct Using an Alpha Channel." |
Video: Photoshop CC: Color Correct Using an Alpha Channel (6:41)
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Apply: Exercise A02-03 - Fix the red face in the photo!
Now that you know several ways to accomplish the same task, does it matter which one you use? No, use whichever technique that gives you the best result. You will find that one of these various techniques will work better with a particular photo than the others - so it's good to know them all.
Now that you know several ways to accomplish the same task, does it matter which one you use? No, use whichever technique that gives you the best result. You will find that one of these various techniques will work better with a particular photo than the others - so it's good to know them all.
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EXERCISE A02-03. The Challenge!
Click here to download the original photo. Apply the Photoshop skills you've just learned! How close can you get to the retouched version below? Save your Photoshop file as A02-03_Your_Name.psd and submit it with the week 2 assignment. Hint: I've used camera raw, Photoshop adjustment layers with the masks, channels, frequency separation retouching, content aware tools, etc. In Photoshop, there are so many ways to do this - it doesn't matter how if you can get to the same end result! |
Original photo
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Restored photo
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