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The Calculations command


Photoshop CS3 Channels & Masks: Advanced Techniques

with Deke McClelland

Video: The Calculations command

In this exercise, I am going to introduce you to one of the oldest commands in all of Photoshop as well as one of the most powerful. That's this command right here, it's under the Image menu, and it's called Calculations. Now what the Calculations command does is it allows you to blend any two channels with each other. So they can be a color bearing channels such as Red, Green, and Blue or they can be alpha channels, and you can blend those two channels together in order to create a new alpha channel. The reason, you would want to do such a thing, is for one thing, to generate a better mask.
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  1. 2h 12m
    1. The Odyssey Continues
      2m 39s
    2. Mapping one image onto another
      7m 12s
    3. Making a custom contrast mode
      7m 9s
    4. Luminance blending
      8m 39s
    5. Forcing the visibility of underlying layers
      4m 3s
    6. Adjusting the appearance of clipped layers
      4m 33s
    7. Selecting a Blend If channel
      6m 11s
    8. Enhancing highlights by hiding them
      5m 8s
    9. Smart Object first, layer mask second
      7m 22s
    10. The Fill Opacity Eight
      4m 30s
    11. Blending Smart Filters
      7m 24s
    12. Cleaning up edges
      7m 38s
    13. More fun with luminance blending
      6m 22s
    14. A first peek at the Calculations command
      12m 11s
    15. Masking a softly focused model
      11m 46s
    16. Moving layers and masks between images
      7m 34s
    17. Matching colors
      9m 12s
    18. Building transitional blended layers
      6m 33s
    19. Restoring normal colors
      6m 49s
  2. 2h 32m
    1. Layer masks, clipping masks, and knockouts
      1m 20s
    2. Rotating and stretching
      7m 54s
    3. A jet of motion blur
      9m 17s
    4. Keyboard tricks
      5m 4s
    5. Merging sky and landscape
      6m 2s
    6. Masking an adjustment layer
      6m 37s
    7. Creating two windows into an image
      7m 42s
    8. Whitening teeth and adding other highlights
      3m 46s
    9. Mapping a texture onto an image
      4m 0s
    10. Isolating a texture with a layer mask
      6m 44s
    11. Welcome to the glass composition
      3m 18s
    12. Balancing shadows and highlights
      5m 51s
    13. Masking the glass
      7m 24s
    14. Masking the text
      9m 23s
    15. Adding and blending the goldfish
      8m 44s
    16. Assembling the perfect group photo
      5m 12s
    17. Aligning photographs automatically
      5m 26s
    18. Masking in each person's best shot
      5m 18s
    19. Masking densely packed people
      6m 17s
    20. Crafting the perfect final poster
      5m 15s
    21. From the improbable to the impossible
      1m 56s
    22. The fantastical "world of clones" effect
      10m 0s
    23. Upsampling and blurring a background
      8m 39s
    24. Adding a knockout mask
      8m 3s
    25. Choking edges with Gaussian Blur and Levels
      3m 46s
  3. 2h 26m
    1. The corrective power of masking
      1m 6s
    2. The amazing luminance mask
      7m 21s
    3. Brightening and neutralizing the eyes
      8m 21s
    4. Adjusting a nondestructive composition
      5m 52s
    5. Creating a corrective mask
      6m 3s
    6. Averaging away irregular flesh tones
      3m 52s
    7. Modifying specific colors
      7m 46s
    8. Initiating the color mask
      5m 59s
    9. Refining the color mask
      6m 39s
    10. Adjusting the edges around fabric
      7m 55s
    11. Perfecting hair
      9m 34s
    12. Sharpening with a High Pass layer
      10m 12s
    13. The also-amazing density mask
      4m 47s
    14. Adjusting the knockout depth
      8m 48s
    15. Fashioning a depth map
      6m 12s
    16. Invoking a depth mask from Lens Blur
      6m 38s
    17. The perfect depth-of-field effect
      6m 25s
    18. Sharpening an archival photograph
      7m 7s
    19. Creating an edge mask
      8m 29s
    20. Making a High Pass sandwich
      7m 45s
    21. Applying the edge mask
      6m 1s
    22. Customizing your sharpening effect
      4m 6s
  4. 2h 3m
    1. Channel Mixer, I am your father!
      1m 39s
    2. Three ways to gray
      7m 48s
    3. Meet the Channel Mixer
      8m 26s
    4. Mixing a custom black-and-white image
      7m 9s
    5. Creating a professional-level sepia tone
      5m 36s
    6. Employing the Black & White command
      8m 0s
    7. Extreme channel mixing
      4m 50s
    8. The infrared photography effect
      6m 42s
    9. Taking shadows to the brink of black
      3m 56s
    10. Elevating highlights, leeching saturation
      5m 58s
    11. Deepening a black-and-white sky
      5m 49s
    12. Infusing luminance levels with color
      5m 43s
    13. Creating an opposing colorization scheme
      4m 58s
    14. Bolstering contrast with the Green channel
      5m 37s
    15. A tiny improvement to a terrific technique
      7m 38s
    16. The simple (but wrong) approach to red-eye correction
      6m 39s
    17. Channel-mixing red pupils
      9m 17s
    18. The expert approach to red-eye correction
      5m 20s
    19. Fixing problem coronas (pupil edges)
      8m 8s
    20. Making pupils match
      4m 7s
  5. 2h 33m
    1. Chops are dead; long live maskops
      1m 36s
    2. The Calculations command
      8m 16s
    3. Blue Screen blending
      7m 40s
    4. Refining the Blue Screen mask
      5m 53s
    5. Brushing away color fringing
      7m 24s
    6. Locking the transparency of a layer
      6m 21s
    7. Nondestructive layer painting
      7m 36s
    8. How the Add blend mode works
      8m 40s
    9. How the Subtract blend mode works
      6m 43s
    10. Focus, noise, and other masking challenges
      5m 32s
    11. The Add mode in action
      7m 51s
    12. The Subtract mode in action
      8m 24s
    13. Comparing two channels with Difference
      5m 23s
    14. Enhancing the contrast with Curves
      9m 10s
    15. Gathering details with Apply Image
      9m 43s
    16. Dodge highlights, burn shadows
      6m 6s
    17. Dodge and Burn in action
      8m 24s
    18. Painting in the scalp
      10m 0s
    19. Painting away the face and chin
      4m 52s
    20. Compositing complementary images
      4m 13s
    21. Multiply, Minimum, Blur, and Apply Image
      6m 40s
    22. Crafting the final composition
      7m 7s
  6. 1h 57m
    1. Mark of the Pen tool
      1m 34s
    2. The big paths project overview
      6m 51s
    3. How to make a path
      8m 24s
    4. Corner points and freeform polygons
      8m 6s
    5. Editing paths with the arrow tools
      5m 2s
    6. Adding and deleting endpoints
      5m 14s
    7. Adding and deleting interior points
      6m 6s
    8. Converting a path to a selection
      3m 35s
    9. Converting a path to a mask
      6m 38s
    10. Smooth points and control handles
      8m 57s
    11. Making cusp points
      5m 59s
    12. Combining paths in a vector mask
      7m 54s
    13. Turning a path into a shape layer
      8m 57s
    14. Combining paths to make a layer mask
      7m 52s
    15. Mixing layer and vector masks
      10m 14s
    16. Editing character outlines as paths
      8m 39s
    17. Using the Convert Point tool
      7m 8s
  7. 3h 17m
    1. Where there's a will, there's a way
      1m 18s
    2. Masking natural cast shadows
      4m 9s
    3. Applying the cast show
      4m 2s
    4. Creating a difference mask
      3m 7s
    5. Applying an arbitrary map
      3m 50s
    6. Making the flesh mask
      7m 16s
    7. Roughing in an object mask
      6m 48s
    8. Drawing missing details with the Lasso tool
      4m 7s
    9. Combining flesh and object masks
      3m 52s
    10. Amplifying the cast shadow
      4m 10s
    11. Selectively choking edges
      3m 58s
    12. Power duplication in Photoshop
      7m 8s
    13. Masking blond hair
      5m 48s
    14. Using Levels to mask iterations
      3m 14s
    15. Drawing an iteration boundary
      4m 54s
    16. Merging the best of two Levels iterations
      4m 4s
    17. More fun with Dodge and Burn
      6m 14s
    18. Fixing edges with the Pen and Stamp tools
      7m 28s
    19. Pulling from another file with Apply Image
      4m 52s
    20. Blending clipped layers independently
      5m 42s
    21. Building the flame mask
      9m 21s
    22. Amplifying the flame
      3m 52s
    23. Masking an image against a busy background
      5m 15s
    24. The Freeform and Magnetic Pen tools
      6m 52s
    25. Masking with arbitrary maps
      9m 32s
    26. A more deliberate approach to arb maps
      10m 51s
    27. Combining arb maps with paths
      9m 28s
    28. Masking with the help of the History brush
      11m 38s
    29. Creating a High Pass mask
      7m 24s
    30. Coloring in the outlines
      8m 31s
    31. Mastering Calculations
      7m 28s
    32. Subtracting and merging the beak
      11m 5s
  8. 1h 33m
    1. The meaning of bit depth (and why you care)
      2m 49s
    2. Scanning line art in 8-bit and 16-bit
      5m 8s
    3. Measuring the 16-bit difference
      8m 8s
    4. Correcting 8-bit images in the 16-bit space
      9m 31s
    5. Opening a raw image directly in 16-bit
      6m 12s
    6. Editing in Camera Raw, opening in 16-bit
      8m 21s
    7. 16-Bit/channel vs. 32-bit/channel (HDR)
      8m 17s
    8. Working with auto-bracketed photographs
      5m 6s
    9. Using the Merge to HDR command
      5m 59s
    10. Adjusting the HDR preview
      6m 0s
    11. Building a 32-bit sky mask
      6m 29s
    12. Properly exposing land and sky
      4m 24s
    13. Modifying a layer mask in 32-bit
      4m 56s
    14. Converting to and correcting in 16-bit Lab
      12m 7s
  9. 2h 8m
    1. Photoshop flirts with the third dimension
      1m 13s
    2. The displacement map
      8m 24s
    3. Making custom waves
      7m 14s
    4. Creating a Gaussian distribution
      4m 31s
    5. Using a two-channel displacement map
      6m 27s
    6. Creating a rustic edge effect
      8m 21s
    7. Distorting and shading with a DMap
      6m 33s
    8. Moonlight reflecting off water
      8m 48s
    9. Mapping the reflection onto the water
      7m 3s
    10. Dipping the moon into the water
      6m 18s
    11. Turning flesh into stone
      7m 55s
    12. Wrapping the stone around the face
      7m 27s
    13. Softening a displacement map
      8m 4s
    14. Making a repeating watermark pattern
      9m 21s
    15. 3D embossing with Lighting Effects
      10m 47s
    16. The amazing credit card type effect
      6m 56s
    17. Lightening the credit card letters
      6m 16s
    18. Wrapping the background around the text
      6m 27s
  10. 1m 43s
    1. Goodbye
      1m 43s

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Watch the Online Video Course Photoshop CS3 Channels & Masks: Advanced Techniques
20h 48m Advanced Nov 21, 2007

Viewers: in countries Watching now:

The elusive alpha channel remains one of the most misunderstood yet powerful tools in Photoshop. Alpha channels are collections of luminance data that control the transparency of an image, and they inform just about every aspect of Photoshop. As he builds transitional blended layers, fashions a depth map, makes edge adjustments, and takes on extreme channel mixing, Omni Award-winning expert Deke McClelland teaches Photoshop users that where there's a will, there's a way. Photoshop CS3 Channels and Masks: Advanced Techniques covers mapping texture on an image, turning flesh into stone, using vector masks, working with all different channels, creating a rustic edge effect, and much more. Exercise files accompany the tutorials.

Download Deke's customized keyboard layouts for Channels and Masks from the Exercise Files tab."

Topics include:
  • Distorting and shading with a DMap
  • Understanding bits and channels
  • Creating paths with the Pen tool
  • Using blend modes and the Dodge and Burn feature
  • Understanding channel mixing
  • Using layer masks, clipping masks, and knockouts
  • Applying Smart Filters
Design Photography
Deke McClelland

The Calculations command

In this exercise, I am going to introduce you to one of the oldest commands in all of Photoshop as well as one of the most powerful. That's this command right here, it's under the Image menu, and it's called Calculations. Now what the Calculations command does is it allows you to blend any two channels with each other. So they can be a color bearing channels such as Red, Green, and Blue or they can be alpha channels, and you can blend those two channels together in order to create a new alpha channel. The reason, you would want to do such a thing, is for one thing, to generate a better mask.

So as opposed to working directly from the Red, Green, or Blue channel, and then enhancing the levels, and overlay painting, and all that good stuff, you can blend two channels together in order to create the base alpha channel and get some additional work done. So you save yourself time plus you can create more details, more articulate, more accurate masks. Now that is, of course, assuming that you come to terms with the way the Calculations dialog box works. It is a little bit complicated but I assure you if you stick with me, you will get a sense of what's going on there and you will become a master masker. This is really an advanced command.

So switch back to the RGB version of the image or you to have the image open and I am not sure that you do because I haven't told you where it is. It's called Model on blue.jpg and it's found inside the 14_Calculations folder. This image comes to us from Klaas Lingbeek- van Kranen of the Netherlands and he works with It features this woman with auburn hair set against a fairly, uniformly blue background, a little darker toward the top than it is at the bottom. She has got a little bit of fly-away hair going on, some softly focused skin. So she is a challenge. Also, she is alternately lighter and darker than her background. So we just can't just say, gosh, she is uniformly lighter or she is uniformly darker than her background as we have with previous sample files. This one, we are going to have to take a different approach, essentially.

So notice here is the Red channel, she is very bright, her skin is very bright, her hair isn't all that contrasty with the background; it's sometimes lighter, sometimes darker. Then dress is also sometimes lighter and sometimes darker than the background. More often than not, it's darker. So in other words, sometimes the foreground image is lighter, sometimes the foreground image is darker than the background. You understand, right? All right, so here is green image; not a lot of contrast going on in the skin tones, dark dress compared with the background, the hair is not a lot of contrast either. The Blue channel, we have the best contrast where the hair is concerned because all of a sudden she is turning into a Brunett, essentially.

Her dress is darker than the background, her skin is a little bit, the edges are a little bit darker than the background but we do have some highlights going on every once in while and, of course, there is not a heck of a lot of contrast. So there is no one channel that's leaping out and saying, "Hey! Choose me, choose me." Instead, we are left with three channels that really aren't any good for establishing a base alpha channel. When you encounter such an image, that's when you think about using the Calculations command. Sometimes, you can use the Color Range command. I have showed you that in the past but other times, when going gets really tough as it does in this image, we have got to resort to Calculations.

Now we are going to mix two channels together, bear that in mind. Of course, then we come to which two channels do you want to mix? More often than not, you want to mix the two channels that are most different from each other. So in other words, you look at these channels and you go, okay Red, she is light, background dark green. Pretty much the same, she and the background are both, sort of, in the mid-tone range. Then Blue, she has got dark hair against the light background. So she is the darkest in this channel and the background is the lightest. So in other words, the channels that are the most different from each other are Red and Blue. This is going to be true anytime you have a model, or a human being, or a portrait shot of any kind, set against the blue background; you are going to talking about merging the Red and Blue channels. If you have a model set against a green background, then you would be wanting to merge the Red and the Green channels with each other, and so on.

Also, if you had a portrait shot of a person against the blue sky, you would also be mixing using the Calculations command, you would be mixing the Red and Blue channels with each other. So once again, you look for the channels that have the highest degree of difference. Then you go up to the Image menu and you choose the Calculations command. Now before I choose this command, I want you to know, in this exercise I am introducing you to the way that the dialog box works. In the next exercise, we will actually use it to build the base alpha channel. So I am going to choose the Calculations command, it brings up a fairly murderous looking dialog box. Not so much because there is all that many options, there are quite a few options here but nothing compared to like Layer Properties where you have more than a 100 options organized in, like, more than ten different panels; that kind of thing. This time you just have a lot of superfluous options and a lot of options that don't make a, heck of, lot of sense.

For starters, Calculations is talking to you in terms of Source 1 and Source 2. What in world does it mean by that? Well, Source 1 is the first channel and Source 2 is the second channel but actually, the way that it works is the Source 2 channel is at the bottom of the stack. So imagine we are putting one channel on top of another channel inside of a layered stack. Source 2 would be at the bottom of the stack and Source 1 would be on top of it. So remember that because that becomes important when we start applying the blend modes down here. It's asking, all right, what image are we working in for starters? Where is the first channel coming from, image and layer wise? Where is the second channel coming from, image and layer wise? Well ostensibly, we are working inside of the same image but you could work inside of a different image. If you have two images open, two or more images open, that are exactly of the same physical size, the same number of pixels wide and tall, then you can select any of those images from this list.

In my case, we want to stick with Model on blue.jpg and for you Model on blue, may be the only image that's open. There is only one layer inside this image, Background. So Layer, in both cases, has to be set to Background. So then, we just ruled out four of the options here. These first two options in Source 1 and the first two options in Source 2, just leave them alone. Next comes Channel, this one is important. Now it's telling you, we are going to merge the two different channels, Red and Blue. So let's go ahead and set Source 1 to Red and we will set Source 2 to Blue. So in other words, Red is going to be sitting on top of Blue. Now, of course, we want to get to a state where she is very bright, including her hair, and her background is very dark.

So far we don't have that. Now inside the Red channel, we do. She is, if I move this out of the way, we can see this little thumbnail back here, she is fairly light in the Red channel and her background is fairly dark, overall, but in the Blue channel, she is, more often than not, darker than her background. So we need to invert the Blue channel and we are going to do that by turning on the Invert check box. Now notice, we get this ghostly image here, against a dark background. That's a good thing. So, more often than not, she is lighter than her background; which is a good thing, by virtue of the fact that we are blending these images together.

Now if at anytime, you want to see one of the channels by itself because right now, we are multiplying them together as per the Calculations dialog box default setting; but if you want to see one or the other by itself, go ahead and switch over to Normal. Now when you choose Normal, you are going to see the Source 1 channel, which is red in this case because it's on top. If you want to see the inverted Blue channel, then change the Opacity value to 0, like so. Then you can see that background channel, essentially here. So always remember, Source 1 on top, Source 2 underneath it.

All right, I am going to change that Opacity value back to 100%. The next option here is Mask, we are going to give that a slip for now, we will come back to it later. Then finally, we have got this guy, Result. What do you want to do with, whatever, you are making here? Which you can preview, by the way, we have got a Preview check box, so we can see what we are doing. Where do you want to put this amalgam of these two channels? The answer is, more often than not, put it inside of a new channel inside this document. You could also generate a selection right after that, if you wanted to or send it to the new document, instead, but we want New Channel which is going to deliver a new alpha channel here inside the Channels palette.

That's it. That's as far as we are going to go inside this exercise. In the next exercise, we are going to investigate, what we can achieve here using the Blending Options in order to generate a base alpha channel, in order, of course, to generate a mask.

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