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Correcting 8-bit images in the 16-bit space

From: Photoshop CS3 Channels & Masks: Advanced Techniques

Video: Correcting 8-bit images in the 16-bit space

In this exercise, we are going to see the effects of editing a continuous tone full color digital photograph in both the 8 bit and 16 bit per channel spaces. Now we are going to see how 16 bit per channel actually provides us with the benefit even if we start things off with an 8-bit per channel JPEG image like this one right here. This image by the way is called Max by water.jpg found inside the 17_16-bit HDR folder. It's a photograph that I shot off my eldest son Max here dipping his toes into Lake Powell and it's actually a beautiful photograph. It's got great colors. We just need to bring those colors to life because right now the luminance is really muted. So we need to increase the contrast and if I were to press Ctrl+L or Command+L on the Mac to bring up the Levels dialog box. You can see that we have a very smooth histogram. The problem is it's all bunched up in the center right there. All the luminance levels are bunched up in this relatively small space.

Correcting 8-bit images in the 16-bit space

In this exercise, we are going to see the effects of editing a continuous tone full color digital photograph in both the 8 bit and 16 bit per channel spaces. Now we are going to see how 16 bit per channel actually provides us with the benefit even if we start things off with an 8-bit per channel JPEG image like this one right here. This image by the way is called Max by water.jpg found inside the 17_16-bit HDR folder. It's a photograph that I shot off my eldest son Max here dipping his toes into Lake Powell and it's actually a beautiful photograph. It's got great colors. We just need to bring those colors to life because right now the luminance is really muted. So we need to increase the contrast and if I were to press Ctrl+L or Command+L on the Mac to bring up the Levels dialog box. You can see that we have a very smooth histogram. The problem is it's all bunched up in the center right there. All the luminance levels are bunched up in this relatively small space.

So we need to bring them out. We need to stretch them apart and we are going to be doing that in this exercise of course. So I am going to go ahead and Cancel out of this dialog box for now and we are going to see the effects of applying our modifications in both 8 bit and 16 bit as I say. So let me Shift+Tab away my palettes and I am going to make a duplicate of this image by going up to the Image menu and choosing the Duplicate command and if you want to see the effects of these modifications you want to do the same thing. So choose the Duplicate command and I am going to go ahead and call this Max 16-bit or something along those lines.

Bear in mind that this is 16 bit so the information per channel per pixel. So on a channel by channel basis. The 8-bit per channel image is really 8+8+8, so it's 24 bits of the information per pixel where as a 16-bit is really 16+16+16 so we have got 48 bits of information per pixel. So I will go ahead and click OK. That's just a function of working inside of a full color RGB file and I am going to go ahead and move Max over a little bit and go to the Window menu and choose Arrange and then I am going to choose this command right there, Tile Vertically.

So we can see the images side by side and I will go ahead and zoom in on Max over here on the right and I need to convert him to 16-bit. So I am going to go up to the Image menu and I am going to choose Mode and I am going to choose 16 Bits/Channel. Now that doesn't spontaneously generate more color information. It just gives you a bigger room to work in. So I frequently make the musical chairs analogy, basically I will go ahead and choose this command here 16 Bits/Channel. Same darn image we have before and the image on left, we have got 256 different chairs and if the color is have to run around the chairs and we take one of the chairs away then two of the colors have to sit on the same chair and one of the colors have to leave the building.

Basically we are harming the image every time we apply a color correction is what it comes down to. If we are working inside of this image we still only have 256 different luminance level per channel but we have got 32000 chairs in the building. So we could sit there all day and take chairs out of the room and you know all the colors get to run around as much as they want. They still get to sit down in independent chairs. So that's all what it does. We just added more chairs to the room essentially inside of this image on right. The number of luminance levels that are occupying the space is still the same. But check it out. Let's go ahead and apply a couple of pretty big corrections here. The first thing I am going to do and I am working on the 8 bit/channel image on left.

I am going to press Ctrl+U or Command+U on the Mac in order to bring up the Hue/Saturation dialog box and I am going to increase the saturation value to 30 okay and you might want to do that as well. Just to bring out some more saturation values here and then click OK and then I am going to go into the Curves dialog box by pressing Ctrl+M or Command+M on the Mac and I am going to go ahead and move this white slider over to an Input level of 170. See that right there.

So 170 is going to 255 and then we will take this black slider and drag it over to the right until the input value becomes 30. So 30 is becoming zero. So we are stretching out the histogram of course. Now that makes Max appear a little too pink in my opinion. So I am going to switch over to the red channel here and I am going to drag the middle. I am going to click in the middle of that line and drag it down slightly in order to remove some of the pink from Max, just a little bit actually. Because we still want a healthy amount of pink in the boy because he is my son. So he is you know fairly pale, except when he gets out he was actually looking fairly sunned in this case but also these rocks tend to be very reddish as well.

So we don't want to subtract too much red and then I am going to go over to the green channel and I am going to click in the center and I am going to drag that up a little bit just to add a little tiny bit of green to the image here and we might want to add a little bit of blue too. You could go ahead and switch over to the blue channel here, then add a little bit of blue if you want to, just to increase the saturation of the blue water here. Then I am going to go back to RGB and really you can apply any modifications you want. These are just ones that I am suggesting. I am going to go ahead and switch back to RGB and I am going to click right about there on the graph and I am going to drag it down in order to darken things up. Fairly precipitously I want to add some heft to this image, make it darker and I think actually this looks pretty good. If you ask me it does. I will go ahead and click OK in order to accept that modification and you can see that we have got this little hint of brown highlight going on from the rocks reflecting in the water. So it's a good looking image actually once we get done modifying it.

But it's a bad looking histogram. Let's press Ctrl+L or Command+L on the Mac to checkout that histogram and you can see that we have got a lot of gaps in this histogram. Meaning that we have a lot of gaps in this histogram meaning that we have a lot of choppy transitions inside of the image. So there is some possible posterization, there might be some color banding as well. Who knows what? But a kind of worst of all in my opinion. If I were to hand this off to a client for example. They would be able to see that I have been in this file and that I applied you know some forms of static color modifications to the image and that I have got a bunch of gaps inside of my histogram. And I am not so sure. I like to share that with clients or anybody for that matter.

I like a nice smooth histogram even when I give an image to you by the way, a little secret. They have got some nice smooth histogram that's because I have monkeyed with the colors carefully. All right, so I am going to go ahead and cancel out of this. Let's go ahead and replay those very same color modifications here inside the 16 bit/channel image. I am going to press Ctrl+Alt+U or Command+Option+U on the Mac in order to replay the Hue/Saturation modification, of saturation plus 30, click OK. Now I am going to press Ctrl+Alt+M or Command+Option+M on the Mac in order to bring up those same Curves modification right here that we have applied before and I will click OK in order to apply the command and you can see it looks the same. Once again this is the same image for all intensive purposes plus we started from the very same file right.

And they look the same on screen because we are viewing the image on essentially 8 bit/channel device. But I am going to press Ctrl+L or Command+L on the Mac. Look at that histogram. It has been modified. It's got some fillers going up there. So it has some gaps on the top end of the histogram but the larger body of the histogram is still in great shape which is basically demonstrating to us that we have smoother transitions. Just by virtue of the fact that we entered 16 bit and applied our color modifications in the 16 bit/channel mode and I will go ahead and cancel out of there.

What I would do at this point. After I have applied my color modifications and I know I am done with those color modifications, I would go up to the Image menu. I would choose Mode and I would choose 8 Bits/Channel in order to convert this image back to an 8 Bits/Channel image because it's silly to leave it in 16 bit; it is not providing us that much utility and that reduces the file size. Notice before I will go ahead and point down to this lower area and 16 bit this image was 46 megs so pretty darn big. After I convert it back to 8 Bits/Channel we can see that it's 23 megabytes essentially and I will press Ctrl+L or Command+L on the Mac. The histogram ends up looking smooth or still.

Now that we have converted back to 8 Bits of data per channel and therefore somebody is going to look at this histogram. That's a the kind of histogram you get with an original unmodified image. No body is really going to know for sure that I have been here and that's what I want. I don't want you to know I have been here. You don't want me to know that you have been there. You know we don't need to know this about each other. All right, anyway we also have smoother color transitions inside this image. So we are going to have less risk of banding and posterization when we go to print. So the moral of the story, even when you are modifying an 8 Bits/Channel image, the JPEG image here, for example, it's a good idea to convert it over to 16 bit color, make your modifications and then convert it back to 8 Bits/Channel and if all you are doing is just modifying the colors in the photograph in order to make them look better. You better off applying those modifications as static modifications from the Image Adjustments menu right here then you are using adjustment layers.

So the technique I just showed you is better than adjustment layers if all you are doing is correcting a standard photograph. All right, in the next exercise, I am going to show you how it gets even better if we open the image into 16 bit in the first place. If we actually start with a 16 bit/channel image.

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This video is part of

Image for Photoshop CS3 Channels & Masks: Advanced Techniques
Photoshop CS3 Channels & Masks: Advanced Techniques

190 video lessons · 26325 viewers

Deke McClelland
Author

 
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  1. 2h 13m
    1. The Odyssey Continues
      2m 39s
    2. Mapping one image onto another
      7m 12s
    3. Making a custom contrast mode
      7m 10s
    4. Luminance blending
      8m 40s
    5. Forcing the visibility of underlying layers
      4m 4s
    6. Adjusting the appearance of clipped layers
      4m 34s
    7. Selecting a Blend If channel
      6m 12s
    8. Enhancing highlights by hiding them
      5m 9s
    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 39s
    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 35s
    17. Matching colors
      9m 13s
    18. Building transitional blended layers
      6m 33s
    19. Restoring normal colors
      6m 50s
  2. 2h 33m
    1. Layer masks, clipping masks, and knockouts
      1m 20s
    2. Rotating and stretching
      7m 54s
    3. A jet of motion blur
      9m 18s
    4. Keyboard tricks
      5m 4s
    5. Merging sky and landscape
      6m 3s
    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 1s
    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 45s
    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 16s
    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 27m
    1. The corrective power of masking
      1m 6s
    2. The amazing luminance mask
      7m 22s
    3. Brightening and neutralizing the eyes
      8m 22s
    4. Adjusting a nondestructive composition
      5m 52s
    5. Creating a corrective mask
      6m 4s
    6. Averaging away irregular flesh tones
      3m 52s
    7. Modifying specific colors
      7m 46s
    8. Initiating the color mask
      6m 0s
    9. Refining the color mask
      6m 40s
    10. Adjusting the edges around fabric
      7m 56s
    11. Perfecting hair
      9m 35s
    12. Sharpening with a High Pass layer
      10m 12s
    13. The also-amazing density mask
      4m 48s
    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 46s
    21. Applying the edge mask
      6m 2s
    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 49s
    3. Meet the Channel Mixer
      8m 26s
    4. Mixing a custom black-and-white image
      7m 10s
    5. Creating a professional-level sepia tone
      5m 36s
    6. Employing the Black & White command
      8m 1s
    7. Extreme channel mixing
      4m 50s
    8. The infrared photography effect
      6m 43s
    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 44s
    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 39s
    16. The simple (but wrong) approach to red-eye correction
      6m 39s
    17. Channel-mixing red pupils
      9m 18s
    18. The expert approach to red-eye correction
      5m 20s
    19. Fixing problem coronas (pupil edges)
      8m 9s
    20. Making pupils match
      4m 8s
  5. 2h 33m
    1. Chops are dead; long live maskops
      1m 37s
    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 22s
    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 33s
    11. The Add mode in action
      7m 51s
    12. The Subtract mode in action
      8m 25s
    13. Comparing two channels with Difference
      5m 24s
    14. Enhancing the contrast with Curves
      9m 11s
    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 1s
    19. Painting away the face and chin
      4m 53s
    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 35s
    2. The big paths project overview
      6m 51s
    3. How to make a path
      8m 25s
    4. Corner points and freeform polygons
      8m 6s
    5. Editing paths with the arrow tools
      5m 2s
    6. Adding and deleting endpoints
      5m 15s
    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
      6m 0s
    12. Combining paths in a vector mask
      7m 55s
    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 10s
    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 17s
    7. Roughing in an object mask
      6m 49s
    8. Drawing missing details with the Lasso tool
      4m 7s
    9. Combining flesh and object masks
      3m 53s
    10. Amplifying the cast shadow
      4m 10s
    11. Selectively choking edges
      3m 58s
    12. Power duplication in Photoshop
      7m 9s
    13. Masking blond hair
      5m 48s
    14. Using Levels to mask iterations
      3m 14s
    15. Drawing an iteration boundary
      4m 55s
    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 29s
    19. Pulling from another file with Apply Image
      4m 52s
    20. Blending clipped layers independently
      5m 43s
    21. Building the flame mask
      9m 22s
    22. Amplifying the flame
      3m 53s
    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 25s
    30. Coloring in the outlines
      8m 31s
    31. Mastering Calculations
      7m 29s
    32. Subtracting and merging the beak
      11m 6s
  8. 1h 33m
    1. The meaning of bit depth (and why you care)
      2m 50s
    2. Scanning line art in 8-bit and 16-bit
      5m 9s
    3. Measuring the 16-bit difference
      8m 9s
    4. Correcting 8-bit images in the 16-bit space
      9m 31s
    5. Opening a raw image directly in 16-bit
      6m 13s
    6. Editing in Camera Raw, opening in 16-bit
      8m 22s
    7. 16-Bit/channel vs. 32-bit/channel (HDR)
      8m 18s
    8. Working with auto-bracketed photographs
      5m 6s
    9. Using the Merge to HDR command
      6m 0s
    10. Adjusting the HDR preview
      6m 0s
    11. Building a 32-bit sky mask
      6m 29s
    12. Properly exposing land and sky
      4m 25s
    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 32s
    5. Using a two-channel displacement map
      6m 28s
    6. Creating a rustic edge effect
      8m 21s
    7. Distorting and shading with a DMap
      6m 34s
    8. Moonlight reflecting off water
      8m 48s
    9. Mapping the reflection onto the water
      7m 7s
    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 5s
    14. Making a repeating watermark pattern
      9m 22s
    15. 3D embossing with Lighting Effects
      10m 48s
    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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