Photoshop CC One-on-One: Fundamentals
Illustration by John Hersey

How luminance works


From:

Photoshop CC One-on-One: Fundamentals

with Deke McClelland

Video: How luminance works

In this movie, I'll introduce you to a few terms and ideas so that you understand how luminance works inside of a digital image. And these ideas will not only help you understand how to correct luminance throughout this chapter, but also when you're working on your own images in the future. I'm working inside a file called luminance demo.psd, it's found inside the 07_luminance folder. Now even though we think of an image as being full-color, it's really a combination of grayscale images working together.
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  1. 38m 23s
    1. Welcome to One-on-One
      1m 51s
    2. Opening from the Windows desktop on Windows 8 (CC 2014)
      6m 16s
    3. Opening from the Windows desktop on Windows 7 or earlier (CC)
      5m 48s
    4. Opening from the Macintosh Finder
      7m 10s
    5. Opening from Photoshop or Bridge
      3m 52s
    6. Opening an image from Mini Bridge (CC)
      2m 39s
    7. Opening through Camera Raw
      5m 11s
    8. Closing one image and closing all
      5m 36s
  2. 52m 47s
    1. Navigating your image
      40s
    2. The dark vs. the light interface
      6m 2s
    3. Navigating tabs and windows
      4m 32s
    4. Panels and workspaces
      6m 20s
    5. Zooming incrementally
      6m 22s
    6. Zooming continuously
      2m 43s
    7. Entering a custom zoom value
      2m 25s
    8. Scrolling and panning images
      2m 31s
    9. Rotating and resetting the view
      2m 11s
    10. Cycling between screen modes
      3m 10s
    11. Using the Navigator panel
      3m 38s
    12. Using Retina and HiDPI displays
      4m 3s
    13. Adjusting a few screen preferences
      8m 10s
  3. 1h 2m
    1. Digital imaging fundamentals
      1m 45s
    2. Image size and resolution
      6m 34s
    3. The Image Size command
      6m 9s
    4. Common resolution standards
      4m 7s
    5. Upsampling vs. real pixels
      7m 59s
    6. Changing the print size
      8m 15s
    7. Downsampling for print
      5m 14s
    8. Downsampling for email
      6m 22s
    9. The interpolation settings
      6m 40s
    10. Downsampling advice
      5m 5s
    11. Upsampling advice
      4m 15s
  4. 53m 21s
    1. The layered composition
      1m 40s
    2. Introducing the Layers panel
      4m 13s
    3. Adding, scaling, and aligning layers
      5m 27s
    4. Dragging and dropping layers
      4m 36s
    5. Stack, reveal, and rename
      3m 1s
    6. Opacity, history, and blend mode
      6m 5s
    7. Duplicating a selected portion of a layer
      5m 32s
    8. Applying a clipping mask
      3m 58s
    9. Blending inside a clipping mask
      4m 10s
    10. Finishing off your artwork
      3m 13s
    11. Creating a new layer and background
      4m 24s
    12. Layering tips and tricks
      7m 2s
  5. 26m 13s
    1. The art of the save
      54s
    2. Four things to know about saving
      5m 59s
    3. Saving layers to PSD
      6m 34s
    4. Saving print images to TIFF
      4m 48s
    5. Saving an interactive image to PNG
      3m 40s
    6. Saving a flat photo to JPEG
      4m 18s
  6. 32m 16s
    1. Honing in on your image
      1m 43s
    2. The new and improved Crop tool
      4m 35s
    3. Editing your last crop
      6m 29s
    4. Cropping to a specific ratio or size
      5m 57s
    5. Straightening a crooked image
      4m 44s
    6. Filling in missing details
      6m 44s
    7. Using the Perspective Crop tool
      2m 4s
  7. 44m 51s
    1. First, there is brightness
      2m 12s
    2. How luminance works
      4m 18s
    3. The three Auto commands
      3m 27s
    4. Automatic brightness and contrast
      6m 5s
    5. The Brightness/Contrast command
      2m 47s
    6. The dynamic adjustment layer
      4m 4s
    7. Editing adjustment layers
      3m 52s
    8. Isolating an adjustment with a layer mask
      3m 31s
    9. Introducing the histogram
      4m 58s
    10. Measuring an adjustment
      3m 34s
    11. Using the Shadows/Highlights command
      6m 3s
  8. 44m 34s
    1. And second, there is color
      1m 31s
    2. Identifying a color cast
      3m 34s
    3. Correcting a color cast automatically
      3m 57s
    4. Changing the color balance
      6m 10s
    5. Compensating with Photo Filter
      3m 11s
    6. Adjusting color intensity with Vibrance
      3m 29s
    7. Correcting color casts in Camera Raw
      5m 46s
    8. The Hue/Saturation command
      5m 26s
    9. Summoning colors where none exist
      4m 9s
    10. Making more color with Vibrance
      4m 27s
    11. Making a quick-and-dirty sepia tone
      2m 54s
  9. 55m 47s
    1. Making selective modifications
      1m 11s
    2. The geometric Marquee tools
      6m 1s
    3. Aligning one image element to another
      4m 59s
    4. The freeform Lasso tools
      3m 59s
    5. The Polygonal Lasso tool and Quick Mask
      5m 19s
    6. Cropping one selection inside another
      6m 15s
    7. Creating rays of light
      4m 44s
    8. Quick Selection and Similar
      4m 11s
    9. Making it better with Refine Edge
      4m 56s
    10. Integrating image elements
      2m 39s
    11. Magic Wand and Grow
      5m 17s
    12. Refine, integrate, and complete
      6m 16s
  10. 53m 48s
    1. Your best face forward
      1m 0s
    2. Content-Aware Fill
      6m 11s
    3. Using the Spot Healing Brush
      5m 36s
    4. The more capable "standard" Healing Brush
      5m 55s
    5. Meet the Clone Source panel
      3m 53s
    6. Caps Lock and Fade
      4m 57s
    7. The Dodge and Burn tools
      5m 1s
    8. Adjusting color with the Brush tool
      6m 35s
    9. Smoothing skin textures
      5m 57s
    10. Brightening teeth
      4m 0s
    11. Intensifying eyes
      4m 43s
  11. 49s
    1. Until next time
      49s

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Watch the Online Video Course Photoshop CC One-on-One: Fundamentals
7h 45m Beginner Jun 28, 2013 Updated Sep 17, 2014

Viewers: in countries Watching now:

Get the ultimate foundation in Adobe Photoshop CC, in this update to the flagship series Photoshop One-on-One. Deke takes you on a personalized tour of the basic tools and techniques that lie behind great images and graphic design, while keeping you up to speed with the newest features offered with Creative Cloud. Learn to open images from multiple sources, get around the panels and menus, and work with layers—the feature that allows you to perform masking, combine effects, and perform other edits nondestructively. Then Deke shows how to perform important editing tasks, such as cropping and straightening images, adjusting the luminance of your image, correcting color imbalances and enhancing color creatively, and finally, retouching and healing.

Topics include:
  • What is color correction?
  • Comparing RGB and CMYK color modes
  • Using grayscales and neutrals for color correction
  • Understanding pixels and bit depth
  • Evaluating and correcting images with histograms
  • Using nondestructive editing tools
  • Removing a color cast
  • Performing curve corrections in Camera Raw
  • Affecting creative adjustments
  • Retouching an image
  • Sharpening images
  • Preparing for print and web use
Subjects:
Design Photography
Software:
Photoshop
Author:
Deke McClelland

How luminance works

In this movie, I'll introduce you to a few terms and ideas so that you understand how luminance works inside of a digital image. And these ideas will not only help you understand how to correct luminance throughout this chapter, but also when you're working on your own images in the future. I'm working inside a file called luminance demo.psd, it's found inside the 07_luminance folder. Now even though we think of an image as being full-color, it's really a combination of grayscale images working together.

And I'll show you what that means in just a moment, but in the meantime know that every pixel has a luminance level, from black at the darkest to white at the brightest, and these ranges of luminance have general names. The darkest luminance levels are known as the shadows, the brightest luminance levels are known as the highlights and then the luminance levels in between are known as midtones. Now there's no specific place at which highlights end and midtones begin, or midtones end and shadows begin.

These are just general ranges of luminance. Now as I was saying, what we see as a full-color image is actually multiple grayscale images working in concert with each other. These grayscale images are known as channels. This image, like all digital photographs contains, three channels, we have a red channel, we have a green channel and we have a blue channel. Where the bright colors in the red and green channels intersect you get yellow. Where the bright colors in the green and blue channels intersect, you get cyan, and where the highlights in the red and blue channels intersect, you get magenta.

Just to give you a sense of how these channels mix to form the full-color image. If you have highlights in all three channels you get white, if you have shadow in all three channels you get black. Now let me show you what the channels look like where this specific image is concerned. I'm going to go up to the Window menu and choose the Channels command in order to bring up the Channels panel which by default lives next door to the Layers panel. And notice that we're seeing what's known as the RGB Composite; that is red, green and blue working together and that the red, green and blue channels are all selected because they're all turned on.

However I can click on any one of these channels to view it independently. So for example, I'll click on the red channel and as you can see, it is a grayscale image. This is what Photoshop sees as it evaluates a full-color image, because Photoshop sees and addresses the image one channel at a time. And as you can see, where this image is concerned, we have tons of highlights inside the red channel. We have a few midtones here and there, but we really don't have anything along the line of shadows.

And just for reference, I'm going to turn that gradient back on, and you can see that the darkest luminance level inside this channel is somewhere around here inside the gradient. So it's by no means black, which is why we have such a washed out image in the first place. Now let's take a look at the green channel, and you can see that things darken up but still not enough, and then here's the blue channel, darker still, but also very bright. All right now, I'll go ahead and switch back to the RGB image and I'll go up to the Image menu and I'll choose a command called Auto Contrast.

And this is one method for correcting the luminance levels inside of an image. And notice that Photoshop darkens up the image considerably and again it does so on a channel-by-channel basis. So every one of these channels is darker. And in fact what Photoshop has done is it's taken the darkest pixels inside the image, which were quite light, and turn them black and then stretch the other luminance levels across the gradient spectrum. And so if I take a look at the red channel now, you can see we've got some very dark shadows inside the pupil, in the eyelashes, and around the iris, and so forth.

The same goes for the green channel, which is darker still, have some very rich shadows going on, and then in the blue channel the same is true except we have more shadow detail than ever. And that friends is how luminance works here inside Photoshop.

Find answers to the most frequently asked questions about Photoshop CC One-on-One: Fundamentals .


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Q: This course was updated on 09/17/2014. What changed?
A: Deke updated the course to reflect changes in the 2014 version of Photoshop CC. This includes everything from opening the program to retouching your photographs with the Healing and Content-Aware tools.
 
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