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Bit depth 101

From: Photoshop CS5 for Photographers

Video: Bit depth 101

For anyone who is interested in photography, or for that matter, for anyone who is interested in creating compelling photographs, well, it's worthwhile to take a few minutes to dig into the topic of the digital image. What exactly is a digital image and how is it made? How is it created? What are the different building blocks that come together to give us what looks like continuous tone photographic quality images? Well, in order to understand the digital image, one of things that we can do is jump back to the time when people when people were trying to come up with a way to create color photographs.

Bit depth 101

For anyone who is interested in photography, or for that matter, for anyone who is interested in creating compelling photographs, well, it's worthwhile to take a few minutes to dig into the topic of the digital image. What exactly is a digital image and how is it made? How is it created? What are the different building blocks that come together to give us what looks like continuous tone photographic quality images? Well, in order to understand the digital image, one of things that we can do is jump back to the time when people when people were trying to come up with a way to create color photographs.

Now, much of color photography is attributed to James Clerk Maxwell. He came up with this idea that he photographed the same image differently. Then he projected these images with red or green or blue colors or filters. What happened was the combination of these three different colors created what look like a color photograph. Now, if someone said that to me today, said, "hey, Chris, I am going to project three different filters, red, green and blue.

I am going to make a color photograph." I would say, "You're crazy. There is no way that's possible." But it's true. This really is the basis for all that we do inside of Photoshop in regards to working with red, green and blue images in this RGB color space. So, really when we are working on our photographs, we are not necessarily working on a color photograph. Rather we are working on the photograph that's a grayscale image with different colors shown through it. The combination of these different colors give us a full-color photograph.

Well, let me explain. Let's dig a little bit deeper. We work in this space, which is the RGB color space. Here in RGB we create colorm hue and tone based on different variables. For example, this color orange here. For the sake of an argument, let's say this was created with a mixture of 240 red, 12 green and 15 blue. It's a combination of these different values which give this pixel its particular color. Again, let's dig a little bit deeper.

Well, the term "pixel" is a concatenation of two words, picture and element. We know that if were to zoom in on a small area of a photograph like the eye here, what we would see would be these little teeny picture elements, these little pixels. It's the combination of all of these little pixels that together give us something that looks like a continuous-tone photograph. Well, how do we actually get these pixels and where do these pixels come from? Well, if were to focus in on say one pixel, that one pixel is based on a bit.

A bit is a binary digit. You may be thinking, okay, this is kind of weird. What is a binary digit? Well a binary digit really is something that you can consider as either on or off. There are two options there. Now, if we add up these options, we can come up with more information. 8 bits is 1 byte, 1024 bytes is 1 KB, 1024 KB is 1 MB, so on and so forth. Well, how then does this relate to us in regards to working in Photoshop? Well, if we have a one-bit pixel, we either have black or white. That's it.

If we have a two-bit pixel, well, then we have few more options. White, gray, dark gray or black. If we go all the way to an 8-bit pixel, we actually have 256 levels of information. The interesting thing is is that when we go to this red, green and blue space, what we have is we have 256 levels of red, times green, times blue, which essentially gives us 16 million color possibilities.

In other words, if we have enough information, if we have eight bits per channel, we then have all of these different variables, all of these different possibilities and options, which ultimately give us the ability to work on images and to create images that have what looks like continuous tone. Well, why then talk about bit depth? Well, bit depth, this whole idea of a grayscale, is going to show up all over the place in Photoshop. In other words, we are going to see it in levels. For example, 0 to 255. Well, 256 levels, right? We can start to understand these levels.

We can understand them based on different channels or based on different controls. We'll see this also in Curves, again, 256 levels here, or we'll see it in places like our Channels panel. Here we have the red channel, the green channel and the blue channel. Here, we see kind of the mystery behind these images ,that it's really a grayscale image with red light being shown through it. Then the combination of the red, and then the green, and the blue, just like James Clerk Maxwell did, then gives us the composite full color photograph, which again has this nice, even and continuous tone.

Well, then if I have to distill this, why learn about bit depth? Well ultimately, what bit depth helps us to do is take images that might look like this, and turn them into something that will look like this. In other words, understanding a bit about bit depth equals better images.

Show transcript

This video is part of

Image for Photoshop CS5 for Photographers
Photoshop CS5 for Photographers

204 video lessons · 43193 viewers

Chris Orwig
Author

 
Expand all | Collapse all
  1. 4m 16s
    1. Welcome
      2m 14s
    2. Using the exercise files
      45s
    3. Photography and Photoshop
      1m 17s
  2. 27m 21s
    1. Becoming a successful student of Photoshop
      1m 1s
    2. Strategies for success
      2m 9s
    3. Taking visual snapshots
      3m 32s
    4. The importance of the 30-minute blink
      2m 38s
    5. Isolation
      5m 41s
    6. Creative memorization
      2m 59s
    7. Say it out loud
      4m 9s
    8. Be prepared for surprises
      1m 17s
    9. Why Photoshop CS5?
      3m 55s
  3. 20m 8s
    1. What is Adobe Bridge?
      2m 51s
    2. Introducing the Bridge workspace
      2m 57s
    3. Using Bridge to review and evaluate photographs
      4m 12s
    4. Working with Bridge and Photoshop
      1m 56s
    5. Introducing Mini Bridge
      3m 49s
    6. Working with Mini Bridge
      4m 23s
  4. 25m 52s
    1. Choosing your color settings
      2m 35s
    2. HUD color picker preferences
      2m 44s
    3. Image interpolation preferences
      3m 52s
    4. Zoom preferences
      1m 47s
    5. Interface preferences
      3m 3s
    6. File-handling preferences
      2m 59s
    7. Performance preferences
      2m 28s
    8. Cursor preferences
      2m 59s
    9. Guides and type preview preferences
      3m 25s
  5. 23m 46s
    1. Introducing color management
      2m 53s
    2. Two simple steps for more accurate color
      5m 34s
    3. Opening and saving files with embedded profiles
      4m 28s
    4. Why color settings and monitor calibration matter
      5m 18s
    5. Creative tip: Setting up your studio
      1m 59s
    6. Monitor calibration
      1m 46s
    7. Color management resources
      1m 48s
  6. 35m 9s
    1. Introducing the Tools panel
      1m 27s
    2. Working with the Tools panel
      4m 36s
    3. Viewing and arranging documents
      4m 29s
    4. Combining multiple images
      4m 15s
    5. Closing multiple images
      2m 17s
    6. Working with panels
      3m 50s
    7. Customizing your workspace
      4m 14s
    8. Creating custom keyboard shortcuts
      4m 49s
    9. Working with the Application bar and Full Screen view
      4m 3s
    10. Working with a Wacom tablet
      1m 9s
  7. 22m 54s
    1. Bit depth 101
      5m 29s
    2. Introducing image size
      3m 26s
    3. Resizing images
      6m 50s
    4. Resizing by cropping
      2m 33s
    5. Straightening an image
      2m 22s
    6. Creative tip: Sizing images correctly
      2m 14s
  8. 33m 49s
    1. Introducing the Camera Raw preferences
      3m 33s
    2. Opening images in Camera Raw
      3m 48s
    3. Using the basic Camera Raw controls
      3m 20s
    4. Color correction and white balance
      3m 7s
    5. Processing multiple images
      2m 21s
    6. Crop and compose
      4m 31s
    7. Converting to black and white
      2m 26s
    8. Camera raw workflow
      7m 36s
    9. Saving images from Adobe Camera Raw
      3m 7s
  9. 38m 9s
    1. Introducing transparency
      1m 29s
    2. Introducing layers
      2m 58s
    3. Working with layers
      3m 49s
    4. Aligning layers
      2m 8s
    5. Creating new layers
      4m 18s
    6. Organizing layers
      3m 34s
    7. Layer style effects
      6m 18s
    8. Creating a clipping mask
      3m 0s
    9. Targeting and moving layers
      4m 10s
    10. Layers shortcuts
      6m 25s
  10. 44m 59s
    1. Using the Magic Wand
      4m 43s
    2. Using the Quick Select tool to remove a background
      2m 16s
    3. Using the Quick Select tool for creative color effects
      2m 23s
    4. Using the Marquee Selection tool
      2m 55s
    5. Using the Magnetic Lasso tool
      3m 6s
    6. Using the Polygonal Lasso tool
      3m 28s
    7. Making color range selections
      3m 35s
    8. Using Refine Edge to improve selections
      3m 17s
    9. Using Refine Edge with a color range
      4m 21s
    10. Introducing paths
      3m 43s
    11. Creating a path selection
      4m 24s
    12. Using a path selection to improve color
      6m 48s
  11. 42m 31s
    1. Introducing masking
      1m 13s
    2. Deconstructing how masking works
      6m 56s
    3. Masking defined
      1m 51s
    4. Refining masked edges
      5m 58s
    5. Building a mask based on color
      6m 11s
    6. Changing a color using a mask
      3m 54s
    7. Masking and selective sharpening
      5m 53s
    8. Using the Mask panel controls
      4m 7s
    9. Quick Mask mode
      6m 28s
  12. 15m 8s
    1. Creating a custom border using masking
      6m 10s
    2. Using pre-built borders
      4m 21s
    3. Exploring sample image frames
      4m 37s
  13. 21m 40s
    1. Introducing the Adjustments panel
      4m 50s
    2. Using Hue/Saturation and the Target Adjustment tool
      4m 29s
    3. Adjusting brightness and contrast
      4m 46s
    4. Working with vibrance and saturation
      3m 31s
    5. Working with adjustment layer presets
      4m 4s
  14. 27m 10s
    1. Introducing levels
      3m 29s
    2. Enhancing color and tone with levels
      6m 32s
    3. Modifying color and contrast with levels
      6m 15s
    4. Using levels to make subjective color shifts
      5m 11s
    5. Using levels and masking
      3m 5s
    6. Creative tip: Checking in
      2m 38s
  15. 34m 14s
    1. Introducing the Curves dialog box
      2m 53s
    2. Demystifying curves
      5m 45s
    3. Using curves to modify color, contrast, and tone
      2m 58s
    4. Combining selections and masking with curves
      3m 6s
    5. Creating hand-painted masks
      4m 27s
    6. Enhancing a portrait with hand-painted masks
      6m 23s
    7. Using curves to enhance color
      4m 24s
    8. Using multiple curves adjustments
      1m 41s
    9. Using, modifying, and saving curves presets
      2m 37s
  16. 23m 5s
    1. Creative tip: Blending two elements
      58s
    2. Introducing blending modes
      2m 26s
    3. Blending modes visualized
      4m 40s
    4. Blending multiple images together
      4m 34s
    5. Using blending modes to remove white or black
      1m 53s
    6. Improving overexposure using blending
      1m 36s
    7. Improving underexposure using blending
      4m 8s
    8. Blending shortcuts
      2m 50s
  17. 16m 40s
    1. Correcting color with the eyedroppers
      4m 58s
    2. Correcting color and tone with the eyedroppers
      4m 14s
    3. Correcting color with Camera Raw
      1m 58s
    4. Camera Raw color correction with a color chart
      1m 52s
    5. Color-correcting skin by the numbers
      3m 38s
  18. 27m 27s
    1. Replacing color
      2m 9s
    2. Replacing color with Hue/Saturation
      5m 12s
    3. Modifying color with Selective Color
      3m 40s
    4. Modifying multiple colors with Selective Color
      3m 5s
    5. Creating dramatic sunset colors
      2m 59s
    6. Using Color Balance to improve sunrise colors
      1m 13s
    7. Using Color Balance, selections, and masks together
      4m 57s
    8. Improving a family portrait with Color Balance
      2m 35s
    9. Creative tip: Shoot more
      1m 37s
  19. 31m 12s
    1. Creative tip: The digital darkroom
      1m 20s
    2. Introducing the Burn and Dodge tools
      3m 22s
    3. Using the Burn and Dodge tools
      3m 31s
    4. Enhancing dimension with the Burn and Dodge tools
      3m 58s
    5. Improving tone with the Burn and Dodge tools
      3m 12s
    6. Using Soft Light for burning and dodging
      5m 58s
    7. Darkening with the Soft Light blending mode
      5m 39s
    8. Adding contrast to the highlights
      4m 12s
  20. 15m 1s
    1. Introducing black-and-white conversion
      4m 9s
    2. Converting a portrait to black-and-white
      4m 22s
    3. Converting a landscape to black-and-white
      2m 18s
    4. Adding grain and tone to a black-and-white image
      2m 39s
    5. Creative tip: Seeing beyond color
      1m 33s
  21. 11m 2s
    1. Adding lens flare
      3m 34s
    2. Adding film grain
      1m 47s
    3. Introducing Smart Filters
      1m 44s
    4. Applying Smart Filters
      3m 57s
  22. 10m 17s
    1. Reducing noise with Surface Blur
      4m 25s
    2. Using the Noise Reduction filter
      2m 56s
    3. Advanced noise reduction using channels
      2m 56s
  23. 45m 18s
    1. Using the Dust and Scratches filter
      3m 8s
    2. Removing dust and scratches with masking
      2m 44s
    3. Introducing the trio of healing tools
      5m 30s
    4. Using the Healing and Clone Stamp tools
      3m 26s
    5. Healing along edges and areas of contrast
      2m 8s
    6. Healing and patching
      5m 19s
    7. Using Content-Aware Fill
      4m 27s
    8. Using multiple content-aware tools for the best results
      4m 19s
    9. Making multiple selections with Content-Aware Fill
      2m 18s
    10. Deleting unwanted elements
      3m 59s
    11. Removing a garment strap with spot healing
      1m 46s
    12. Cleaning up an image with spot healing, cloning, and healing
      6m 14s
  24. 48m 59s
    1. Creative tip: Leaving crumbs
      1m 18s
    2. Whitening teeth
      2m 8s
    3. Improving eyes
      3m 24s
    4. Changing eye color
      2m 48s
    5. Enhancing makeup
      5m 33s
    6. Removing blemishes
      2m 20s
    7. Softening skin
      7m 0s
    8. Reducing shadows around eyes
      5m 32s
    9. Reducing and removing wrinkles around eyes
      6m 43s
    10. Improving highlights and shadows
      5m 6s
    11. Changing body size and shape with Liquify
      3m 50s
    12. Modifying the body with Puppet Warp
      3m 17s
  25. 23m 19s
    1. Using the Lens Correction filter
      5m 16s
    2. Removing distortion with Automatic Lens Correction
      2m 22s
    3. Improving a portrait with Lens Correction
      2m 16s
    4. Using Free Transform to correct perspective
      4m 47s
    5. Using Puppet Warp to correct perspective
      4m 47s
    6. Changing a portrait with Puppet Warp
      3m 51s
  26. 37m 11s
    1. Introducing Smart Sharpen
      4m 56s
    2. Smart Sharpen demystified
      5m 49s
    3. Smart Sharpen and masking
      8m 49s
    4. Using Smart Sharpen on small details
      5m 3s
    5. Using the Unsharp Mask filter
      6m 9s
    6. High Pass sharpening an image
      6m 25s
  27. 20m 5s
    1. Resizing for the web and email
      4m 23s
    2. Sharpening for the web and email
      2m 49s
    3. Correcting color for the web and email
      3m 50s
    4. Saving and exporting images for the web and email
      2m 43s
    5. Creating a web gallery
      4m 0s
    6. Sharing photos online
      2m 20s
  28. 17m 15s
    1. Desktop printing recommendations
      2m 46s
    2. Creating a PDF layout and contact sheets
      3m 5s
    3. Resizing and sharpening for a specific print size
      3m 12s
    4. Using Soft Proof to preview the print
      3m 48s
    5. Using the Print dialog box
      2m 25s
    6. Choosing printer settings
      1m 59s
  29. 56s
    1. Goodbye
      56s

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