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Photoshop CS4 Essential Training

Reading histograms


From:

Photoshop CS4 Essential Training

with Jan Kabili

Video: Reading histograms

You may have heard the term histogram and be wondering exactly what it means. In Photoshop, the Histogram is a panel that contains a bar chart that represents the distribution of tones in an image. If you know how to read a histogram, it can be useful when you're correcting colors and tones in a photograph. In this movie, I'm going to explain how the histogram works in Photoshop and show you some examples of photographs that have different kinds of histograms. If your Histogram panel isn't open, go to the Window menu at the top of the screen and choose Histogram, or you can change to the Color and Tone workspace from the Workspace menu, as I've done here.
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  1. 2m 31s
    1. Welcome
      1m 27s
    2. Using the example files
      1m 4s
  2. 25m 14s
    1. Touring the interface
      4m 25s
    2. Working with tabbed documents
      5m 15s
    3. Using tools efficiently
      3m 51s
    4. Arranging panels
      3m 53s
    5. Customizing keyboard shortcuts
      2m 50s
    6. Saving a custom workspace
      3m 0s
    7. Changing screen modes
      2m 0s
  3. 19m 3s
    1. Touring the Bridge interface
      6m 31s
    2. Opening images from Bridge
      1m 20s
    3. Reviewing images
      4m 42s
    4. Finding images
      6m 30s
  4. 44m 53s
    1. Setting preferences
      4m 23s
    2. Choosing color settings
      8m 11s
    3. Zooming and panning
      5m 27s
    4. Resizing and image resolution
      3m 17s
    5. Adding to the canvas
      2m 2s
    6. Rotating the canvas
      1m 44s
    7. Choosing color
      4m 49s
    8. Sizing a brush tip
      3m 4s
    9. Undoing and the History panel
      5m 0s
    10. Saving and file formats
      3m 29s
    11. Creating a file from scratch
      3m 27s
  5. 37m 58s
    1. Making geometric selections
      6m 14s
    2. Modifying selections
      4m 43s
    3. Combining selections
      3m 16s
    4. Using the Quick Selection tool
      5m 34s
    5. Refining selection edges
      4m 12s
    6. Using Quick Mask mode
      2m 18s
    7. Selecting with the improved Color Range command
      4m 32s
    8. Selecting with the Magnetic Lasso tool
      2m 28s
    9. Using the Background Eraser tool
      3m 7s
    10. Saving selections
      1m 34s
  6. 39m 56s
    1. Understanding layers
      5m 43s
    2. Creating layers
      5m 12s
    3. Working in the Layers panel
      2m 19s
    4. Locking layers
      4m 17s
    5. Working with multiple layers
      4m 6s
    6. Merging and flattening layers
      3m 55s
    7. Adding a shape layer
      4m 43s
    8. Basic layer masking
      4m 23s
    9. Using layer blend modes and opacity
      5m 18s
  7. 23m 19s
    1. Cropping
      3m 26s
    2. Straightening
      3m 17s
    3. Transforming
      4m 42s
    4. Working with Smart Objects
      6m 48s
    5. Using Content-Aware Scaling
      5m 6s
  8. 1h 10m
    1. Reading histograms
      4m 21s
    2. Using adjustment layers and the Adjustment panel
      6m 4s
    3. Adjusting tones with Levels
      7m 49s
    4. Limiting adjustments with layer masks
      5m 40s
    5. Using masks in the new Masks panel
      6m 9s
    6. Limiting adjustments by clipping
      3m 6s
    7. Adjusting with Shadow/Highlight
      5m 7s
    8. Adjusting with Curves
      7m 37s
    9. Adjusting with Hue/Saturation
      3m 42s
    10. Adjusting with Vibrance
      2m 16s
    11. Removing a color cast
      4m 26s
    12. Using the Black & White adjustment layer
      2m 39s
    13. Using the Dodge Burn and Sponge tools
      4m 11s
    14. Reducing noise
      2m 39s
    15. Sharpening
      4m 42s
  9. 38m 0s
    1. Using the Spot Healing Brush tool
      5m 17s
    2. Using the Healing Brush tool
      5m 51s
    3. Using the Patch tool
      4m 52s
    4. Using the Clone Stamp tool
      4m 8s
    5. Enhancing eyes
      9m 29s
    6. Changing facial structure
      5m 0s
    7. Softening skin
      3m 23s
  10. 44m 38s
    1. What's a raw image?
      4m 25s
    2. Touring the Camera Raw interface
      7m 35s
    3. Working in the Basic panel
      7m 54s
    4. Working in the Tone Curve panel
      2m 21s
    5. Working in the HSL/Grayscale and Split Toning panels
      3m 46s
    6. Looking at the other Camera Raw panels
      3m 45s
    7. Using the Adjustment Brush tool
      4m 2s
    8. Using the Graduated Filter tool
      3m 56s
    9. Working with multiple files
      6m 54s
  11. 21m 6s
    1. Using the Brushes panel
      8m 30s
    2. Filling with color
      3m 49s
    3. Replacing color
      4m 14s
    4. Using gradients
      4m 33s
  12. 16m 55s
    1. Working with point type
      9m 59s
    2. Working with paragraph type
      3m 17s
    3. Warping text
      3m 39s
  13. 25m 23s
    1. Adding a layer style
      4m 6s
    2. Customizing a layer style
      3m 35s
    3. Copying a layer style
      3m 5s
    4. Creating a new style
      3m 32s
    5. Using Smart Filters
      5m 22s
    6. Working in the Filter Gallery
      5m 43s
  14. 13m 14s
    1. Auto-blending focus
      4m 47s
    2. Creating Photomerge panoramas
      4m 2s
    3. Combining group photos
      4m 25s
  15. 23m 27s
    1. Creating an action
      7m 16s
    2. Batch processing with an action
      6m 36s
    3. Using the Image Processor
      9m 35s
  16. 29m 20s
    1. Printing
      11m 32s
    2. Making a contact sheet from Bridge
      6m 12s
    3. Creating a web gallery from Bridge
      7m 17s
    4. Preparing photos for the web
      4m 19s
  17. 30s
    1. Goodbye
      30s

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Photoshop CS4 Essential Training
7h 55m Beginner Oct 13, 2008

Viewers: in countries Watching now:

Photoshop has become an indispensible tool for photographers, designers, and all other creative professionals, as well as students. Photoshop CS4 Essential Training teaches a broad spectrum of core skills that are common to many creative fields: working with layers and selections; adjusting, manipulating, and retouching photos; painting; adding text; automating; preparing files for output; and more. Instructor Jan Kabili demonstrates established techniques as well as those made possible by some of the new features unique to Photoshop CS4. This course is indispensable to those who are new to the application, just learning this version, or expanding their skills. Example files accompany the course.

Topics include:
  • Learning and customizing the interface and workspace
  • Utilizing various manual and guided selection techniques
  • Working with Adobe Camera Raw
  • Adding special effects with layer styles and Smart Filters
  • Creating Photomerge panoramas
  • Optimizing photos for the web and creating web galleries
Subject:
Photography
Software:
Photoshop
Author:
Jan Kabili

Reading histograms

You may have heard the term histogram and be wondering exactly what it means. In Photoshop, the Histogram is a panel that contains a bar chart that represents the distribution of tones in an image. If you know how to read a histogram, it can be useful when you're correcting colors and tones in a photograph. In this movie, I'm going to explain how the histogram works in Photoshop and show you some examples of photographs that have different kinds of histograms. If your Histogram panel isn't open, go to the Window menu at the top of the screen and choose Histogram, or you can change to the Color and Tone workspace from the Workspace menu, as I've done here.

I usually go to the panel menu on the Histogram and change it from its default Compact View to Expanded View. Right now the histogram is showing us information about all the color channels in the special Colors view. To make it easier to read, I'm going to change the Channel menu there to look at an RGB Composite View. So what is the histogram? As I mentioned it's a bar chart that represents the distribution of tones in the open image. The left side of the chart represents the darkest tones in an image. The right side of the chart represents the brightest tones in an image and the area between represents all the possible gray tones in an image.

This black mound here represents the actual tonal values in the open photograph. If you could pull this mound apart, you would see it's made up of individual vertical bars. Each of those bars is above a particular point on the graph. Where there is a tall bar, that means there is a relatively large amount of that particular tone in the image, and where there are no bars, that means there's none of that particular tone. Every photograph will have a different histogram. You don't always want a histogram that looks like this, but many photographs do look best if they have a wide range of tones.

Those photographs like this one will have a histogram that runs across the entire Histogram panel. But let's take a look at some other kinds of photographs and their histograms. I'm going to click on the second tab that I have open here. The over.psd image. You can see by looking at it that this is a very bright image. If you look at the histogram for this photograph, you'll see that all of its tones are indeed over at the white side of the bar graph. There are very few grays and no blacks at all. Let's look at the clipped.psd image.

The foreground of this photograph looks fine, but as you can see, many of the clouds are pure white, lacking in detail. That's represented on this histogram by this spike on the far right. If you have a spike in an image, that's usually not a good thing because it means you have lost detail, either in the highlights if the spike is there or in the shadows if the spike is over here. You'll notice something else in this histogram. There's a yellow triangle here. That means that the histogram has changed and needs to be updated. You see this in Histogram panel when you make an adjustment to an image.

To update the histogram you can click on this double curved arrow and the yellow warning symbol will go away. Let's take a look at a really dark image. Its histogram is located primarily in the dark area, but there is a lot of middle gray too. If you'll notice in the Layers panel, there are two layers in this image. The top layer is composed only of this dark bank building. I can set the histogram to show me just the tones in a single selected layer by going to its Source menu and choosing Selected Layer instead of Entire Image.

Watch how the histogram changes when I do that. Now as expected, we see that all of the pixels are over on the left side representing just the dark pixels in the bank layer. I'd like to show you one more image and that is this one, flat.psd. I find the histogram particularly useful on an image like this, because when I look at it, I can see that it doesn't look very good. But I'm not necessarily sure how to fix it. It helps me to see in the histogram that all of the pixels in this image are concentrated in the gray tones in the middle. That means it doesn't have much contrast.

In other words, it doesn't have white whites and black blacks. So, if I wanted to correct this image I would probably do a Levels or a Curves adjustment, trying to expand this tonal range and get some whites and blacks and different shades of gray into the photograph. The histogram really is a useful tool that can help you to analyze an image when you're beginning to edit it and to understand what your edits are doing as you make them. Now that you've seen a few examples of different kinds of photographs and their histograms, I hope you'll be better able to read the histograms on your own images.

Find answers to the most frequently asked questions about Photoshop CS4 Essential Training.


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Q: How can artwork be transferred from Photoshop CS4 to Illustrator CS4 without the background?
A: Save the image in Photoshop’s native PSD format. The background in Photoshop must be transparent, meaning there should be no background layer. (To remove a background layer, move your artwork to a separate layer by selecting and copying the content, minus the background, to a new layer, and then delete the background layer. A checkboard pattern behind your image indicates transparent pixels.) 
 


In Illustrator, select File > Open, and select the PSD file. In Photoshop Import dialog box, select Convert Layers to Objects.

Q: How do I retouch an image I have of an old photograph I scanned?
A: There are a few courses that address image restoration. Check out the Photoshop CS4 Portrait Retouching Essential Training course, and for problems dealing specifically with old photographs, watch the Restoration movies in chapter 15 of the Enhancing Digital Photography with Photoshop CS2. Additionally, learn how to research and date photos with our Growing and Sharing Your Family Tree course.
Q: A client has asked for artwork to be delivered as JPEGs or BMP files in 16-bit format. In Photoshop CS4, there does not appear to be an option to save an image as a 16-bit JPEG. Is there a way to save JPEG files as 16-bit in Photoshop?
A: Unfortunately, JPEGs cannot be saved in 16 bit. JPEGs, by nature, are 8-bit. So if you open a high-bit image into Photoshop CS4, you will see no option in any of the save dialog boxes to save the file as a JPEG. You would first have to convert the image to 8 bit (by choosing Image > Mode > 8 bits/channel) and then save it as an 8-bit JPEG. If you open a high-bit image into Photoshop CS5, you will see the option to save it as a JPEG in the Save, Save As, and Save for Web dialog boxes.  But the JPEG will not be saved as 16-bit. Instead, Photoshop will downsample it to 8-bit for you  before saving it as JPEG.
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