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How color channels work

From: Photoshop Masking and Compositing: Fundamentals

Video: How color channels work

In this exercise, we're going to take a look at how channels work. I still have open Toucan with swatches.psd; I also have the Channels panel open as you can see. Now I happen to be working in the RGB color mode. RGB stands for red green, blue, by the way, and as a result, the top item in the Channels list reads RGB. I stress that this top item is not in and of itself a channel; it's actually a composite view of three channels working together. And those three channels are red, green and blue, which are the component color bearing channels.

How color channels work

In this exercise, we're going to take a look at how channels work. I still have open Toucan with swatches.psd; I also have the Channels panel open as you can see. Now I happen to be working in the RGB color mode. RGB stands for red green, blue, by the way, and as a result, the top item in the Channels list reads RGB. I stress that this top item is not in and of itself a channel; it's actually a composite view of three channels working together. And those three channels are red, green and blue, which are the component color bearing channels.

I say color bearing, to distinguish them from the so-called Alpha channels, which are these masks down at the bottom of the list. And notice, neither of the masks is currently selected, but all the channels are selected, because we're saying once again the color composite view. If you want to take a look at the independent channels, just go ahead and click on one of them. So, for example, when I click on red, I see the red channel independently of green and blue. When I click on green, I see it independently of red and blue and then when I click on blue, I see it independently of red and green.

You also have access to these keyboard shortcuts Ctrl+3, Ctrl+4 and Ctrl+5, that's Command+3, Command+ 4 and Command+5 on the Mac for the independent channels. And if you want to switch back to the full color composite, you can press Ctrl+2 on the PC or Command+2 on the Mac. Now the reason that I'm showing you these channels is because they are key to getting masking done inside of Photoshop. If it weren't for each one of these independent color channels, I never would have been able to generate this mask around the bird, and therefore I would not have been able to color its background.

Because I can access these channels, I was able to mask the bird in color of the background with impunity. Now you may have seen when we're working in the independent channels, we are seeing grayscale versions of the image. So it's a little difficult to gauge where the colors went, and what kind of contribution each one of these channels is making. So if you're working along with me, go and switch back to the full color composite, switch to the Layers panel and notice we have a couple of groups that work here. If I turn on the bird labels, I'll see a series of color labels throughout the photograph, and those will help me keep track of where I am color wise inside of the independent channels.

Notice that some of the labels list the colors brightness, for example, we have medium green, we have dark green as well, and some of them don't. If you don't see a brightness that means we're seeing the color pretty much as bright as it gets. I also have these color swatches up here in the upper left corner. I have some labels for them as well that you can get to by turning on that top group. And I want you to note here that each one of these colors is cranked up to its absolute full brightness value and its full intensity.

And as a result they're highly saturated, very bright colors. In case you're unfamiliar cyan is a 50- 50 mix of green and blue and magenta is a 50-50 mix of red and blue. Yellow, by the way, is a 50 -50 mix of red and green. Now that may seem a little weird, but bear in mind when you're working inside of an RGB image you're working with the primary colors of light. Light that's been captured by a digital camera and light that's being projected by your monitor.

And as a result, adding primary colors, such as red and green goes ahead and creates a brighter color, in this case, yellow. All right, let's take a look at these channels independently. I am going to switch back to the Channels panel, and I'm going to click on red. Anywhere where we're seeing darkness or shadows, results in little participation of the red channel. So we are not getting much light out of the red channel in the black regions of the bird and we won't get any participation from the other channels either, that's why that region looks black.

We are going to get absolute participation in the white area and we are going to see brightness and the other channels there as well. We're also going to see a lot of red in yellow areas, whether it's a bright yellow or a medium yellow, like the one down here at the bottom of the screen. And we'll see bright pixels inside the orange areas and the tip of the bill which is red as well. We're not going to see too much going on inside the green regions, we are seeing quite a bit of red in the background, especially down here in the violet region. Now notice the color swatches.

Red is very instrumental in communicating, red, orange, yellow and magenta and it engages to a certain extent inside the violet swatch. There is no red inside that green swatch or the cyan and blue swatches. All right, now let's take a look at the green channel. Now notice the amazing thing about the green channel is it comes closest to being a straightforward grayscale representation of the image. So we have a nice distribution of shadows and highlights throughout this channel. Again, the black area is black, the white area is white.

I was telling you that yellow is a combination of red and green light, so the yellow areas are very bright. We also have some brighter pixels going on for the greens; however, we're really dropping out in the reds. The background is about as bright as it was when we were looking at the red channel, and then check out the swatches here. We've got big participation inside the yellow and green swatches, as well as the cyan swatch in the second row. We have a little bit going on where orange is concerned, nothing for red and nothing for blue, violet or magenta either.

All right, next comes the blue channel. The blue channel is always going to be the one that looks the worst inside of a digital photograph, and as a result it can sometimes give you some very interesting results where masking is concerned. Because, after all it is that very, very different view of the image, than you're used to. Notice that most of the bird is going very, very dark, because there's not much blue action inside any of these colors, with the exception of that shoulder which is brighter here in the blue channel, than it is in the other two.

Also notice this cyan area around the eye is fairly bright in the blue channel; in the red channel it's extremely dark. And then we have a little bit of brightness going on here inside the white region, which implies that that area isn't actually truly white, it's probably more of a pale yellow. Notice that the background has brightened up considerably, both at the top and the bottom of the image, and the entire bottom row of swatches are lit up, the entire top row of swatches that is red, orange, yellow and green have gone totally dark.

All right, so hopefully that gives you an introductory sense anyway of how color bearing channels contribute to the overall color of an image. However, at this point, my biggest question if I were watching this, would be how in the world do a bunch of grayscale images end up mixing together and creating a full-color view, and I'll explain exactly how that works in the next exercise.

Show transcript

This video is part of

Image for Photoshop Masking and Compositing: Fundamentals
Photoshop Masking and Compositing: Fundamentals

128 video lessons · 30964 viewers

Deke McClelland

Expand all | Collapse all
  1. 15m 25s
    1. Welcome
      1m 12s
    2. Loading my custom dekeKeys shortcuts
      3m 45s
    3. Adjusting the color settings
      4m 29s
    4. Setting up a power workspace
      5m 59s
  2. 1h 0m
    1. The channel is the origin of masking
      1m 54s
    2. The Masks and Channels panels
      4m 48s
    3. How color channels work
      7m 7s
    4. Viewing channels in color
      3m 24s
    5. How RGB works
      4m 12s
    6. Single-channel grayscale
      5m 12s
    7. Mixing a custom "fourth" channel
      5m 15s
    8. The other three-channel mode: Lab
      5m 45s
    9. A practical application of Lab
      4m 55s
    10. The final color mode: CMYK
      7m 5s
    11. Introducing the Multichannel mode
      5m 56s
    12. Creating a unique multichannel effect
      5m 18s
  3. 44m 27s
    1. The alpha channel is home to the mask
      1m 40s
    2. The origins of the alpha channel
      3m 40s
    3. How a mask works
      7m 10s
    4. Making an alpha channel
      4m 2s
    5. Using the new channel icons
      6m 27s
    6. Saving an image with alpha channels
      4m 23s
    7. Loading a selection from a channel
      4m 7s
    8. Putting a mask into play
      3m 55s
    9. Loading a selection from a layer
      4m 27s
    10. Loading a selection from another image
      4m 36s
  4. 1h 0m
    1. The mask meets the composition
      1m 8s
    2. Viewing a mask as a rubylith overlay
      6m 13s
    3. Changing a mask's overlay color
      5m 34s
    4. Painting inside a mask
      6m 3s
    5. Cleaning up and confirming
      5m 18s
    6. Combining masks
      5m 10s
    7. Painting behind and inside a layer
      5m 27s
    8. Blending image elements
      6m 1s
    9. What to do when layers go wrong
      6m 3s
    10. Hiding layer effects with a mask
      4m 22s
    11. Introducing clipping masks
      5m 29s
    12. Unclipping and masking a shadow
      3m 50s
  5. 1h 35m
    1. The seven selection soldiers
    2. The marquee tools
      6m 31s
    3. The single-pixel tools (plus tool tricks)
      6m 48s
    4. Turning a destructive edit into a layer
      5m 34s
    5. Making shapes of specific sizes
      7m 7s
    6. The lasso tools
      5m 49s
    7. Working with the Magnetic Lasso tool
      7m 19s
    8. The Quick Selection tool
      8m 13s
    9. Combining Quick Selection and Smudge
      4m 52s
    10. The Magic Wand and the Tolerance value
      6m 55s
    11. Contiguous and Anti-aliased selections
      6m 58s
    12. Making a good selection with the Magic Wand
      6m 34s
    13. Selecting and replacing a background
      6m 55s
    14. Resolving edges with layer effects
      7m 52s
    15. Adding lines of brilliant gold type
      7m 28s
  6. 1h 11m
    1. Selections reign supreme
    2. Introducing "selection calculations"
      4m 19s
    3. Combining two different tools
      7m 29s
    4. Selections and transparency masks
      5m 17s
    5. Selecting an eye
      7m 1s
    6. Masking and blending a texture into skin
      5m 1s
    7. Painting a texture into an eye
      4m 19s
    8. Combining layers, masks, channels, and paths
      4m 54s
    9. Moving selection outlines vs. selected pixels
      5m 36s
    10. Transforming and warping a selection outline
      7m 45s
    11. Pasting an image inside a selection
      7m 26s
    12. Adding volumetric shadows and highlights
      6m 54s
    13. Converting an image into a mask
      4m 42s
  7. 1h 5m
    1. The best selection tools are commands
      1m 5s
    2. Introducing the Color Range command
      5m 59s
    3. Working in the Color Range dialog box
      7m 7s
    4. Primary colors and luminance ranges
      4m 12s
    5. A terrific use for Color Range
      4m 57s
    6. Introducing the Quick Mask mode
      7m 43s
    7. Moving a selection into a new background
      5m 43s
    8. Smoothing the mask, recreating the corners
      8m 43s
    9. Integrating foreground and background
      4m 44s
    10. Creating a cast shadow from a layer
      2m 51s
    11. Releasing and masking layer effects
      3m 11s
    12. Creating a synthetic rainbow effect
      4m 30s
    13. Masking and compositing your rainbow
      4m 46s
  8. 1h 17m
    1. The ultimate in masking automation
      1m 6s
    2. Introducing the Refine Mask command
      6m 58s
    3. Automated edge detection
      8m 23s
    4. Turning garbage into gold
      6m 19s
    5. Starting with an accurate selection
      7m 11s
    6. Selection outline in, layer mask out
      7m 48s
    7. Matching a scene with Smart Filters
      4m 29s
    8. Cooling a face, reflecting inside eyes
      4m 45s
    9. Creating a layer of ghoulish skin
      4m 28s
    10. Adding dark circles around the eyes
      5m 20s
    11. Creating a fake blood effect
      5m 38s
    12. Establishing trails of blood
      7m 40s
    13. Integrating the blood into the scene
      7m 3s
  9. 1h 48m
    1. Using the image to select itself
      1m 37s
    2. Choosing the ideal base channel
      5m 7s
    3. Converting a channel into a mask
      6m 34s
    4. Painting with the Overlay mode
      7m 27s
    5. Painting with the Soft Light mode
      5m 55s
    6. Mask, composite, refine, and blend
      4m 40s
    7. Creating a more aggressive mask
      7m 2s
    8. Blending differently masked layers
      7m 0s
    9. Creating a hair-only mask
      6m 0s
    10. Using history to regain a lost mask
      3m 42s
    11. Separating flesh tones from hair
      8m 28s
    12. Adjusting a model's color temperature
      4m 30s
    13. Introducing the Calculations command
      7m 22s
    14. Extracting a mask from a Smart Object
      6m 34s
    15. Integrating a bird into a new sky
      5m 40s
    16. Creating synthetic rays of light
      6m 4s
    17. Masking and compositing light
      7m 39s
    18. Introducing a brilliant light source
      7m 5s
  10. 1h 34m
    1. The synthesis of masking and compositing
      1m 36s
    2. White reveals, black conceals
      6m 45s
    3. Layer masking tips and tricks
      5m 8s
    4. Generating a layer mask with Color Range
      5m 38s
    5. The Masks panel's bad options
      5m 18s
    6. The Masks panel's good options
      3m 50s
    7. Creating and feathering a vector mask
      3m 42s
    8. Combining pixel and vector masks
      3m 50s
    9. Working with path outlines
      7m 10s
    10. Combining paths into a single vector mask
      7m 52s
    11. Sharpening detail, reducing color noise
      4m 27s
    12. Recreating missing details
      8m 49s
    13. Masking glass
      5m 50s
    14. Refining a jagged Magic Wand mask
      5m 53s
    15. Masking multiple layers at one time
      5m 15s
    16. Establishing a knockout layer
      6m 6s
    17. Clipping and compositing tricks
      7m 37s
  11. 1m 17s
    1. Next steps
      1m 17s

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