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Measuring the 16-bit difference

From: Photoshop CS3 Channels & Masks: Advanced Techniques

Video: Measuring the 16-bit difference

All right, glad to see you back for more here because this is kind of a tough topic to wrap your mind around. So we have got an 8 bit per channel image open here on the left and a 16 bit per channel image open here on the right. The images in question are Pen&ink (8bit). jpg and Pen&ink(16bit).tif and they are both found inside of the 17_16bitHDR folder, just to keep things simple. To go ahead and throw them in the folder called 17_16bit_HDR that will simplify things. Anyway it's our folder naming convention so there you go but I have got these two images open there and functionally identical scans. Well, at least they are scans of the exact same artwork. And they are both scanned using the same model scanner the only difference is I saved one of the scans in the 8 bit per channel space and I saved the other scan in the 16 bit per channel. So we have up to 256 different brightness values over here on the left and we have as many as upwards of 32000 brightness values over here on the right.

Measuring the 16-bit difference

All right, glad to see you back for more here because this is kind of a tough topic to wrap your mind around. So we have got an 8 bit per channel image open here on the left and a 16 bit per channel image open here on the right. The images in question are Pen&ink (8bit). jpg and Pen&ink(16bit).tif and they are both found inside of the 17_16bitHDR folder, just to keep things simple. To go ahead and throw them in the folder called 17_16bit_HDR that will simplify things. Anyway it's our folder naming convention so there you go but I have got these two images open there and functionally identical scans. Well, at least they are scans of the exact same artwork. And they are both scanned using the same model scanner the only difference is I saved one of the scans in the 8 bit per channel space and I saved the other scan in the 16 bit per channel. So we have up to 256 different brightness values over here on the left and we have as many as upwards of 32000 brightness values over here on the right.

We probably don't actually have that many brightness values but we could have that many, put it that way. But it's safe to say, we don't have any more than 256 over here on the left and we have probably a couple of thousand really over here on the right and that's going to make a big difference when we go to edit the image and the edit that we need to apply, we need to increase the contrast of these images so that the dark lines are black, absolutely black and the white areas are absolutely white instead of gray as they are right now, these light gray areas.

So, let's go ahead and use the Levels command, I am going to first make sure that the image on left is active then I am going to press Ctrl+L or Command+L on the Mac to bring up the Levels dialog box and you can see this histogram right there and notice that there is essentially three different lumps in the histogram. This lump over here, this guy right there, that represents the dark lines inside of my artwork so that's the actual Pen&ink work and then this big hump over here on the right represents page white, this area right there and then this hump that represents all of those gray diagonal lines that are holding the photos into place on the photo album page.

So here is what we are going to do, I am going to increase the black point value beyond that first hump, well beyond it, in fact, I am going to take that black point value up to a 115 so anything with the luminance level of a 155 or darker becomes black and then I am going to drag the white slider not just beyond page white. Notice that leaves the photo album down here at the bottom of the screen. Let's go ahead and take it beyond the next hump as well which makes the photo album lines disappear. Good, and I am going to take the White Point Value down to a 150 so anything with a luminance level of a 150 or lighter becomes white. So all we have left is this little range of luminance levels right there that's going to get stretched across the entire histogram.

All right, I will go ahead and click OK to apply that modification. Now let's go over to Pen&ink(16bit).tif and I want you to press Ctrl+Alt+L or Command+Option+L on the Mac in order to replay that exact same levels modification. So notice it's taking to me using the exact same values as before as if zero is black, which is true in 16 bit as well but 255 for white that is strictly an 8 bit per channel convention it doesn't apply to 16 bit, it would be 32000 something for white and Levels goes ahead and talks to me in 8 bit per channel language no matter what bit depth I am working with. And that's true for a lot of commands inside of Photoshop.

They talk to you in 8 bit language even if you are working on a 16 bit per channel image but rest assured you are working on a 16 bit per channel image as you will see very shortly. So anyway exact same modification being applied and the two images as a result, I will go ahead and click on the OK button in order to accept that modification, look the same. They look the same before the modification, they look the same after the modification. The reason being of course, that we are viewing the images on a 8 bit per channel display device and so the device really can't show us the difference between these two images but we can see the difference between the two images using a histogram.

So check this out, I will go back to the original image and we might as well use the histogram in the Levels dialog box so I will press Ctrl+L once again and check that out. Notice these little whiskers down here at the bottom of the screen. Those represent all the gray values that are available to us and then this big line over here represents black and this big line over here represents white. Now the problem is that Photoshop goes ahead and scales everything in between so they just appear as tiny little whiskers even though there is tons of gray pixels inside of this image.

So what we are better off doing is selecting only the gray pixels and measuring them. And here is how we are going to do that, go ahead and cancel out of this dialog box. I want you to go over to the Magic Wand tool, grab the Magic Wand tool her from the toolbox and make sure these settings are enforced; The Tolerance value should be zero, Anti- Alias should be turned off, Contiguous off, Sample All Layers off, so all the check boxes off this time around Tolerance zero. And now click in the white pixel and that will select all of the white pixels inside of the image. Now I want you to press the Shift key and I want you to click on a black pixel like, let's click inside of the guys eye, sort of towards the middle of the eye. So Shift+Click on a Black pixel and that selects all of the Black pixels as well. So now all of the black pixels are selected and all of the white pixels are selected. None of the Gray pixels are selected.

Now I want you to go up to the select menu an chose Inverse. Now you don't have any White pixels or Black pixels selected, you only have gray pixels selected. And you can see the marching ants, go ahead and press Ctrl+H or Command+H on the Mac so that the marching ants stop animating on screen there. Then press Ctrl+L or Command+L on a Mac and those are your remaining gray values. Notice that they look like columns or at least longer hairs separated by big areas of space and those big areas of space represent gaps in the histogram areas where there are no continuous colors so we do not have continuous colors anymore. We have posterization, pretty bad posterization in fact as well. Go ahead and click Cancel in order to cancel out that dialog box, let's run through those same steps here in the 16 bit per channel image.

So I have gone ahead and selected all the white pixels, I am going to Shift+Click on the black pixels to select all of the black pixels as well. And then I am going to go up to the Select menu and choose the Inverse command and now only the gray pixels are selected inside the image, neither black nor white just the gray pixels in between. I am going to press Ctrl+H or Command+H on the Mac to stop animating the marching ants and then I am going to press Ctrl+L and get a load to this. Ctrl or Command+L, a nice full rich histogram. So we still have more than 256 luminance levels available inside of this image, despite our drastic modification.

As a result this image on right, even though it doesn't look any better on screen, is going to hold up better to further editing because at some point we would start noticing the difference and it's going to print better as well and it's going to up sample better and down sample better and everything else. Anything else you care to do it inside of Photoshop is going to go better, thanks to the fact that we are working with a 16 bit per channel image. So the practical up shot in this case is when you are scanning black and white line art always scan to 16 bit per channel, then any modifications that you make inside of Photoshop are essentially, really, non-destructive modifications, you are going to have a hard time, harming this image where you are going to have a very easy time harming the one over here on the left.

All right, so that's just an introduction to 16 bit. We are going to see more 16 bit color this time applied to a continuous tone full color photograph in the next exercise.

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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 · 26575 viewers

Deke McClelland
Author

 
Expand all | Collapse all
  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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