Understanding Histogram display mode

When you switch from Shooting Information display mode to the Histogram display mode, you see the data shown in Figure 4-15. Again, you get the thumbnail view of your image, but this time some of the extensive shooting data is replaced by a second histogram.

The next two sections explain what information you can glean from the histograms. See the preceding sections for a map to the other shooting data on the screen.

RGB histogram

RGB histogram

Brightness histogram

Figure 4-15: Histogram display mode replaces some shooting data with an RGB histogram.

Brightness histogram

Figure 4-15: Histogram display mode replaces some shooting data with an RGB histogram.

Interpreting a brightness histogram

One of the most difficult photo prob lems to correct in a photo editing program is known as blown highlights in some circles and clipped highlights in others. In plain English, both terms mean that highlights — the brightest areas of the image — are so overexposed that areas that should include a variety of light shades are instead totally white. For example, in a cloud image, pixels that should be light to very light gray become white due to overexposure, resulting in a loss of detail in those clouds.

In Shooting Information display mode, areas that fall into this category blink in the image thumbnail. This warning is a great feature because simply viewing the image on the camera monitor isn't always a reliable way to gauge exposure; the relative brightness of the monitor and the ambient light in which you view it affect the appearance of the image onscreen.

For a detailed analysis of the image exposure, check the Brightness histogram, which is a little graph that indicates the distribution of shadows, highlights, and midtones (areas of medium brightness) in your image, as shown in Figure 4-16.

Photographers use the term tonal range to describe this aspect of their pictures. The Brightness histogram appears to the right of the image thumbnail in Shooting Info display mode and in the lower right corner in Histogram display mode.

The horizontal axis of the graph represents the possible picture brightness values, from the darkest shadows on the left to the brightest highlights on the right. And the vertical axis shows you how many pixels fall at a particular brightness value. A spike indicates a heavy concentration of pixels. For example, in Figure 4-16, which shows the histogram for the image in Figure 4-15, the histogram shows a fairly broad range of brightness values, but few pixels at the maximum brightness or shadow values.

Understanding Histogram


Figure 4-16: The Brightness histogram indicates the tonal range of your image.


Figure 4-16: The Brightness histogram indicates the tonal range of your image.

Keep in mind that there is no one "perfect" histogram that you should try to achieve. Instead, you need to interpret the histogram with respect to the amount of shadows, highlights, and midtones that comprise your subject. For example, the histogram in Figure 4-15 makes sense for this particular image because the subject itself contains few very white or black areas — hence the lack of pixels at either end of the histogram. You should pay attention, however, if you see a very high concentration of pixels at the far right or left end of the histogram, which can indicate a seriously overexposed or underexposed image, respectively.

Reading an RGB histogram

When you view your images in Histogram display mode, you see two histograms: the Brightness histogram, covered in the preceding section, and an RGB histogram, shown in Figure 4-17.

To make sense of the RGB histogram, you first need to know that digital images are called RGB images because

Coloured Histograms Back Canons
Figure 4-17: The RGB histogram can indicate problems with color saturation.

they are created out of three primary colors of light: red, green, and blue. The RGB histogram shows you the brightness values for each of those primary colors.

By checking the brightness levels of the individual color components, sometimes referred to as color channels, you can assess the picture's color saturation levels. If most of the pixels for one or more channels are clustered toward the right end of the histogram, colors may be oversaturated, which destroys detail. On the flip side, a heavy concentration of pixels at the left end of the histogram indicates an image that may be undersaturated.

A savvy RGB histogram reader can also spot color balance issues by looking at the pixel values. But frankly, color-balance problems are fairly easy to notice just by looking at the image itself. And understanding how to translate the histogram data for this purpose requires more knowledge about RGB color theory than I have room to present in this book.

ir If you are a fan of RGB histograms, however, you may be interested in another possibility: You can swap the standard Brightness histogram that ■ appears in Shooting Information playback mode with the RGB histogram.

Just visit the Playback menu, highlight the Histogram option, as shown in Figure 4-18, and press the Set button to display the right screen in the figure. Select RGB instead of Brightness and press the Set button again.

mis H «s

Protect images


Erase images

Print order

Transfer order

Histogram Brightness

Histogram Brightness

Auto play


Figure 4-18: You can change the histogram type that appears in Shooting Information playback mode.

Figure 4-18: You can change the histogram type that appears in Shooting Information playback mode.

For information about manipulating color, see Chapter 6.

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  • Haddas
    How to put histogram display in canon 1000d?
    8 years ago
    How to use the histogram on a canon rebel XS?
    8 years ago
  • battista
    How do I display histogram on canon EOS Rebel?
    8 years ago
  • Luke
    How to read RGB histogram?
    8 years ago
    Where to find histogram in canon eos 1000d?
    6 years ago
  • Semrawit
    Where to change the histogram setting on the canon rebel xsi?
    6 years ago
  • Dorotea Monaldo
    How to remove the graph from image viewer of canon 1000d?
    3 years ago
  • prima
    How to remove histogram on canon 1000d?
    3 years ago
  • giulia
    How to remove Rgb mode in Canon 1000d?
    3 years ago
  • Kyllikki
    How program histogram on rebel t2i?
    2 years ago
  • curzio
    How to display histagram canon rebel xs?
    1 year ago
  • Berylla
    What information can you glean from this histogram?
    3 months ago

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