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Inventing a Red channel with Lab

From: Photoshop CS4 One-on-One: Advanced

Video: Inventing a Red channel with Lab

All right, I'd like you start things off by opening this image called Dive master.jpg. Don't worry about the others for now. I have just got them up in case I want to show where we're going. This is that just hideous image. If you can fix this image, you can fix the colors in anything, let me tell you. So that's the proposition I make to you. Now we are going to start things off by inventing a red channel. If you recall, that's our big problem we have no red channel. And come to speak of it, we don't really have a good green channel. We've got no shadows. Basically the darkest colors are light mid tones and I wouldn't even go so far as to say we have mid tones in the blue channel. We have some odd hot highlights sitting here. So nothing really about this image is in good shape.

Inventing a Red channel with Lab

All right, I'd like you start things off by opening this image called Dive master.jpg. Don't worry about the others for now. I have just got them up in case I want to show where we're going. This is that just hideous image. If you can fix this image, you can fix the colors in anything, let me tell you. So that's the proposition I make to you. Now we are going to start things off by inventing a red channel. If you recall, that's our big problem we have no red channel. And come to speak of it, we don't really have a good green channel. We've got no shadows. Basically the darkest colors are light mid tones and I wouldn't even go so far as to say we have mid tones in the blue channel. We have some odd hot highlights sitting here. So nothing really about this image is in good shape.

Now there are ways to invent color and that's what we've got to do. I want to make this very clear. We are going to have to fake this image because the camera did not deliver us anything to work with in terms of reds or oranges or really yellows. The yellowish color we have is fairly chartreuse right here. We're missing an entire end of the spectrum. So we've got to make it up. Now there are good ways to make up color and there are bad ways to make up color. I want to show you a powerhouse function here that turns out to be not a really great way to make up color and that's the Lab mode and I point to the Lab mode because once you know a thing or two about lab it's tempting the user for things like this because it doesn't think in terms of red, green and blue.

The notion is that since it doesn't think that way you can invent red out of whole cloth. So here's how we're going to do it. First of all I want you to note something. This is just by way of an FYI. See that asterisk that's up there in the Title Bar. That asterisk can either appear inside the parenthesis or outside over here to the right of the parenthesis. If it's on the outside of the parenthesis then that means that you have unsaved changes, that you need to press Ctrl or Command S in order to update your image. If it's on the inside that means you're working in a color space other than the ones that you had established inside the Color Settings dialog box.

Whereas way back at the beginning of the fundamental series I advice you to go ahead and establish Adobe RGB as your default RGB environment. This image was shot in sRGB as is typical with Point and Shoot cameras. I just went ahead and left it that way. I didn't convert it. I mean their colors are in terrible shape. So it's really not going to help us out that much. So it might as well stick in sRGB and Photoshop is entirely capable of handling multiple colors bases at the same time. It doesn't break us right over it. And I also want you to know what happens when we go up to the Image menu, choose Mode and choose Lab Color. Why the asterisk switches places? It's now on the outside because we have unsaved changes because we just switched the color model and also it's not on the inside of the parenthesis because it can't be.

Unlike RGB which has different flavors and CMYK which has different flavors, there is one and only one lab inside Photoshop. So here we are, we're in the Lab mode now. Notice we've got a Lightness channel and an A and a B, and got information and there is A, there is B. They never look all that great. So the fact they are looking as ungreat as ever is not that troubling. And Lightness you know all we have is light mid tones and highlights. No surprise there. That's really all we had in the first place and here's our composite image.

All right, so since this is ostensibly a chapter about adjustment layers, let's go ahead and apply one. So we'll go to the Adjustments palette right here and let's just go ahead and a Levels layer. I'm just going to click the Levels dialog box and I could go ahead and click on Auto or something just to bring these guys tight to the ends of the histogram. So we've now darkened our shadows and we've lightened our highlights and I could back off for the darkening just a little bit maybe, but generally speaking everything is pretty good. Let's go ahead and up the Gamma value a little bit by pressing Shift+Up Arrow after clicking inside over there, and now we have a Gamma value of 1.1, fine.

All right, things are little more complex here inside the A and B channels. Now what I want you to know is here's the deal with a lab image. You always have a cone of luminance levels but if things were balanced, this guy would be centered right there on the gray triangle or nearly, very nearly centered on it. It would not be completely on the left side of the Gray slider triangle there. We should have some pinks. Notice we have no pinks whatsoever. Not a single pink. No surprise because in order to get pinks you've got to have red channel. So we've got nothing over there. It's all greens inside of this particular channel.

All right, so let's monkey with things. Let's go ahead and bring these guys over. You can't Auto inside this channel so you just have to drag these guys around and ooh look at that. Suddenly we do have an operational red inside of this photograph. Great! All right, so now let's switch over to B and this time we do have a few yellows because yellows after all, they also reside in the green channel, and then we've got not surprisingly lots and lots of blues. All right, so again let's just make just a change that we wouldn't dare make. I mean this is really over the top. Scooting these slider triangles in this bar. But to what degree do we want to make this image kind of yellowish? Notice that I'm getting quite the green flavor now out of the image. Let's go back to A and back off of the green and see what we end up getting. All right, that's entertaining if nothing else, now I'm not really too concerned about what exact values you apply right here. You can be playful. Have fun. The colors don't look particularly realistic at this point. But whatever.

Let's go ahead and hide the Adjustments palette just so that we can focus on the Layers palette for a moment here. Now I want to switch back to RGB just so that we can see what we brought. What kind of channels do we have now? So let's go up to the Image menu, choose Mode and choose RGB Color. That is going to want to flatten our adjustment layer right here. Notice that it's saying, hey! changing modes, and by modes it means color models in this case, will discard an adjustment layer. Change mode anyway? And so it's telling you, if you click OK it's going to throw the layer away. It's just going to throw in the trash. So don't click OK, click Flatten, this is what you want. The other option is Cancel, which of course is going to leave you in the Lab mode. So you want Flatten so you keep the results, your wonderful results of your modifications here.

So point there is adjustment layers do not survive color transformations. You cannot take adjustment layers from the RGB mode to the Lab mode to CMYK and so forth. You're going to have to dispose them when you do that. The reason is because think about it, what would that levels adjustment we just made in Lightness A and B, what would it even mean in RGB? How would that translation occur? It couldn't occur. There is no way we could even fake it as an adjustment layer inside of RGB. So of course it doesn't attempt to do so. It either throws it away or flattens.

All right, now let's go to Channels palette. Look at here. We've got a red channel, a completely respectable red channel. When I say respectable, it looks better than the green and blue channels, did just a moment ago. Meanwhile green looks pretty awesome. And the blue channel looks like the blue channel. I mean we've lost some highlights here and we've got some awfully dark shadows but it's kind of a gummy channel to begin with. But red, I'm just amazed by red. All right, let's go back to RGB and just for laughs, go up to the Image menu and choose Auto Color in order to just make the red channel even that much better. And now notice- look at that red channel. Oh! It's so good looking.

Where did it come from? And here's green. Looking pretty much the same and same with blue. Those channels didn't get modified too much. All right, so back to RGB. Wow! We invented a red channel out of whole cloth. From nothing we made a red channel. It's not the least but accurate. The effect doesn't look right at all. Not dark- green skin, and his flippers here and the rest of his -- the colors of his dive outfit were not bright pink. He is a brave man but I don't know if he's that brave and then finally he was not floating around the Emerald City.

So these colors are completely imaginary. As well they will be. We have to invent imaginary colors because we don't have the red colors to work with. But this is not the way to perform our big act of fakery. What we really want to do is stay in RGB, that's the mode for us, and use this wonderful function that we haven't seen so far called the Channel Mixer, and I'm going to show you how it works in the next exercise.

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This video is part of

Image for Photoshop CS4 One-on-One: Advanced
Photoshop CS4 One-on-One: Advanced

218 video lessons · 24071 viewers

Deke McClelland

Expand all | Collapse all
  1. 22m 32s
    1. Welcome to Photoshop CS4 One-on-One Advanced
      1m 43s
    2. Installing the DekeKeys keyboard shortcuts
      6m 17s
    3. Resetting the function keys on a Mac
      3m 51s
    4. Installing the CS4 color settings
      4m 37s
    5. Setting up the CS4 color settings
      6m 4s
  2. 2h 43m
    1. Highlights, shadows, and midtones
    2. Low contrast, bad meter
      5m 57s
    3. Auto tone, contrast, and color
      8m 1s
    4. Cache levels and the Histogram palette
      7m 16s
    5. How the auto commands work
      10m 15s
    6. A first look at Levels
      6m 11s
    7. Target colors and clipping
      9m 6s
    8. Modifying input levels
      9m 44s
    9. Adjusting the gamma value
      7m 34s
    10. Previewing clipping
      7m 17s
    11. The futility of output levels
      4m 56s
    12. Channel-by-channel edits
      11m 54s
    13. When levels fail
      4m 34s
    14. A first look at Curves
      8m 46s
    15. Static Curves layer tricks
      7m 45s
    16. Dynamic Curves layer tricks
      7m 25s
    17. Correcting the composite image
      8m 30s
    18. Neutralizing a color cast
      6m 52s
    19. The Target Adjustment tool in Curves
      8m 29s
    20. Correcting an image in Lab
      10m 7s
    21. The Shadows/Highlights filter
      4m 18s
    22. Radius and tonal width
      8m 11s
  3. 1h 48m
    1. Edge-enhancement tricks
      1m 13s
    2. How sharpening works
      3m 48s
    3. The single-shot sharpeners
      4m 29s
    4. The Unsharp Mask filter
      7m 57s
    5. Understanding the Radius value
      6m 25s
    6. Gauging the best settings
      7m 47s
    7. Previewing how sharpening will print
      3m 37s
    8. Measuring and setting screen resolution
      6m 56s
    9. Tweaking the screen resolution
      4m 28s
    10. Sharpening the luminance data
      8m 23s
    11. USM vs. Smart Sharpen
      4m 23s
    12. Smart Sharpen's Remove settings
      5m 50s
    13. High-resolution sharpening
      6m 16s
    14. When to leave More Accurate off
      3m 48s
    15. When to turn More Accurate on
      4m 23s
    16. The advanced options
      7m 57s
    17. Saving Smart Sharpen settings
      4m 23s
    18. Accounting for camera shake
      7m 7s
    19. Sharpening with the High Pass filter
      9m 8s
  4. 2h 16m
    1. Why would you blur?
      1m 8s
    2. Fading after an undo
      3m 27s
    3. The "bell-shaped" Gaussian Blur
      5m 43s
    4. The linear Box Blur
      3m 6s
    5. Add Noise vs. Median
      4m 50s
    6. Despeckle vs. Dust & Scratches
      6m 31s
    7. Smart Blur vs. Surface Blur
      8m 13s
    8. The Motion Blur filter
      4m 33s
    9. Radial Blur's Spin and Zoom variations
      5m 48s
    10. Mixing filtered effects
      3m 56s
    11. The "Captain Kirk in Love" effect
      5m 4s
    12. Diffusing focus with Blur and Overlay
      8m 50s
    13. Simulating Vaseline and film grain
      8m 2s
    14. Filling a layer with a neutral color
      2m 55s
    15. Old-school contrast reduction
      3m 39s
    16. Three steps to diffused focus
      7m 36s
    17. Averaging skin tones
      9m 45s
    18. Addressing the stubborn patches
      5m 26s
    19. Combining Gaussian Blur and Average
      6m 1s
    20. Blurring surface details
      3m 2s
    21. Smoothing blemishes while matching noise
      8m 6s
    22. Reducing digital noise
      8m 47s
    23. Striking a smooth/sharpen compromise
      4m 36s
    24. Smoothing over JPEG artifacts
      7m 38s
  5. 2h 31m
    1. Independent layers of color adjustment
      1m 7s
    2. Undersea color channels
      4m 2s
    3. Inventing a Red channel with Lab
      8m 20s
    4. Mixing color channels
      6m 55s
    5. Making shadows with Levels
      7m 5s
    6. Applying small color adjustments
      6m 0s
    7. Further modifying Levels in Lab
      8m 50s
    8. Creating a dynamic fill layer
      4m 38s
    9. Brushing and blending color
      4m 42s
    10. Working with "found masks"
      7m 31s
    11. Saturation, sharpen, and crop
      8m 9s
    12. Mixing a monochromatic image
      7m 2s
    13. Masking an adjustment layer
      4m 45s
    14. Working with Opacity and blend modes
      3m 39s
    15. Adding a black-and-white adjustment
      5m 53s
    16. The Target Adjustment tool in black and white
      6m 12s
    17. Tinting a monochrome photo
      3m 19s
    18. Introducing Gradient Map
      4m 17s
    19. Adjusting both color and luminance
      5m 44s
    20. Infusing elements with different colors
      6m 22s
    21. Adjustment layers as creative tools
      4m 33s
    22. Inverting and brightening the background
      5m 14s
    23. Blurring live, editable type
      5m 43s
    24. Hue, saturation, and darkness
      6m 51s
    25. Filling type with a color adjustment
      3m 24s
    26. Using one adjustment to modify another
      3m 21s
    27. Breathing color into the title
      3m 38s
    28. The Hue/Saturation humanoid
      3m 44s
  6. 1h 48m
    1. Parametric operations
      1m 23s
    2. The power of blend modes
      6m 16s
    3. Changing the Opacity value
      5m 46s
    4. Opacity vs. Fill Opacity
      4m 37s
    5. Meet the blend modes
      6m 4s
    6. Blend mode shortcuts
      7m 8s
    7. Darken, Multiply, and the Burn modes
      6m 33s
    8. Tempering a Burn effect with Fill
      4m 43s
    9. Saving a blended state
      4m 18s
    10. Lighten, Screen, and the Dodge modes
      8m 22s
    11. Linear Burn = Add minus white
      5m 31s
    12. Overlay and the contrast modes
      6m 52s
    13. Fill Opacity takes priority
      6m 19s
    14. Difference and exclusion
      5m 21s
    15. Using difference for golden highlights
      4m 2s
    16. The composite (HSL) modes
      6m 8s
    17. The brush-only modes: Behind and Clear
      10m 31s
    18. Layer groups and the Pass Through mode
      8m 54s
  7. 1h 53m
    1. It's all about the presentation
    2. Moving a layer a specific number of pixels
      6m 59s
    3. Adding a pixel mask to a layer
      5m 48s
    4. Editing a layer mask
      7m 19s
    5. Combining layers into a clipping mask
      6m 19s
    6. Introducing the Advanced Blending options
      4m 45s
    7. Using the luminance blending sliders
      7m 26s
    8. Forcing through underlying luminance
      4m 32s
    9. Masking with a path outline
      5m 45s
    10. Refining a mask from the Masks palette
      7m 18s
    11. Creating and modifying a layer group
      3m 29s
    12. Establishing a knockout group
      5m 29s
    13. Fixing last-minute problems
      6m 23s
    14. Introducing layer comps
      6m 40s
    15. Exploring layered states
      6m 43s
    16. Deleting layers and updating comps
      6m 18s
    17. Saving a basic composition
      6m 21s
    18. Assigning and saving appearance attributes
      7m 15s
    19. Layer comps dos and don'ts
      7m 27s
  8. 1h 56m
    1. Type: The great imaging exception
    2. Establishing default formatting attributes
      4m 5s
    3. Saving formatting attributes as a preset
      8m 5s
    4. Making a point text layer
      6m 18s
    5. Editing size and leading
      6m 44s
    6. Working with vector-based text
      6m 12s
    7. Formatting area text
      4m 16s
    8. Creating a layer of area text
      3m 20s
    9. Resizing the text frame
      4m 34s
    10. Changing the anti-aliasing setting
      3m 58s
    11. Obscure but important formatting options
      6m 31s
    12. Text editing tricks and shortcuts
      8m 44s
    13. Creating a cast shadow
      6m 1s
    14. Blurred shadows and beveled text
      7m 16s
    15. Drawing a path outline
      4m 51s
    16. Creating type on a path
      6m 39s
    17. Flipping text across a circle
      3m 18s
    18. Vertical alignment with baseline shift
      4m 16s
    19. Warping text
      4m 57s
    20. Scaling your text to taste
      3m 33s
    21. Applying a custom warp
      6m 24s
    22. Creating an engraved text effect
      5m 11s
  9. 2h 17m
    1. Bending an image to fit your needs
    2. Creating a canvas texture
      6m 48s
    3. Masking objects against a white background
      5m 42s
    4. Scaling an image to fit a composition
      8m 9s
    5. Aligning one layer to fit another
      3m 51s
    6. Changing the Image Interpolation
      8m 10s
    7. Merging faces
      5m 32s
    8. Rotating the first clock hand
      7m 17s
    9. Adding hands and pasting styles
      6m 40s
    10. Series duplication in Photoshop
      4m 35s
    11. Masking objects against a black background
      6m 34s
    12. Skews and perspective distortions
      7m 57s
    13. Envelope-style warps
      9m 2s
    14. Old-school distortion filters
      8m 50s
    15. Introducing the Liquify filter
      4m 9s
    16. Reconstructing an image
      6m 55s
    17. Using the Warp tool
      5m 16s
    18. The Pucker and Bloat tools
      5m 53s
    19. Push, Turbulence, and Twirl
      6m 41s
    20. The Freeze and Thaw mask tools
      5m 45s
    21. Saving and loading a mesh file
      3m 59s
    22. Creating and applying a texture layer
      8m 30s
  10. 1h 28m
    1. Effects vs. styles
      1m 11s
    2. Of layer styles and masks
      4m 37s
    3. Everything about drop shadow
      8m 2s
    4. Adding a directional glow
      4m 39s
    5. Colorizing with Color Overlay
      5m 18s
    6. Stroke and fill opacity
      5m 48s
    7. Creating a multicolor Outer Glow
      9m 22s
    8. Introducing Bevel and Emboss
      7m 48s
    9. Contour and Texture
      4m 35s
    10. Simulating liquid reflections
      6m 28s
    11. Saving layer styles
      6m 18s
    12. Applying and appending styles
      4m 36s
    13. Saving and swapping style presets
      3m 16s
    14. The five effect helpers
      3m 47s
    15. Blending the effect before the layer
      5m 1s
    16. Colorizing a signature
      3m 30s
    17. Clipping an effect with a mask
      4m 5s
  11. 1h 50m
    1. Welcome to the digital darkroom
      1m 46s
    2. Opening Camera Raw in the Bridge
      5m 44s
    3. The Camera Raw 5 interface
      4m 39s
    4. Adjusting the white balance
      5m 0s
    5. Finessing and saving changes
      7m 55s
    6. Using the White Balance tool
      2m 43s
    7. Working with the Exposure controls
      7m 34s
    8. Straightening and cropping a raw image
      5m 53s
    9. Applying automatic exposure adjustments
      6m 6s
    10. Exposure warnings
      5m 44s
    11. Clarity, Vibrance, and Saturation
      4m 47s
    12. Using the Graduated Filter tool
      3m 33s
    13. Dodging with the Adjustment brush
      9m 24s
    14. Tone Curve adjustments
      6m 54s
    15. Using the Spot Removal tool
      2m 48s
    16. Removing noise and sharpening detail
      4m 5s
    17. Adjusting HSL values
      4m 18s
    18. Adjusting luminance, color by color
      4m 14s
    19. Black and white and split toning
      5m 16s
    20. Camera Raw tips and tricks
      7m 32s
    21. Correcting JPEG and TIFF images
      4m 42s
  12. 57s
    1. Until next time

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