How to Read a Color Histogram

Опубликовал Admin
26-08-2021, 06:10
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A histogram is a useful graph that shows you how a picture's brightness correlates to the number of pixels in it. They can be found on some camera settings and on your photo editing software. Histograms most often show up as blue, red, or green peaks depending on which tones are the most present in your photo. By looking at the histogram's peaks, or the upside-down 'U' shapes, you can figure out if your picture is well-balanced and what you can do to make the colors and exposure even better.

Understanding the Graph

  1. Look at the horizontal axis to understand the picture’s brightness. The horizontal line at the bottom of the histogram, also called the x-axis, represents the tones of your photo. There are 255 different tones that a picture can be made up of, with the darkest tones on the left end of the horizontal axis and the lightest tones on the right side of the axis.
    • For example, a color tone of 0 would be black and at the far left, while 255 is on the far right and is white. The numbers in between represent the rest of the colors.
  2. Refer to the vertical axis to understand the number of pixels. The line going up the histogram vertically, or the y-axis of the graph, tells you how many pixels there are. This shows you the number of pixels that have the level of brightness corresponding to the x-axis. The more pixels there are for a specific color tone, the more that color shows up in your photo.
  3. Identify peaks on the left side that indicate a photo with low brightness. If your histogram has a big peak on the far-left side of the graph, this means that your photo is made up of a lot of shadows or black tones. Photos that have low brightness are also called “low key.”
    • Since the left side of the histogram starts with 0 (the blackest tone), if you see a peak on this side it means the majority of the pixels are this color.
    • For example, maybe you took a picture of the woods at night. This picture would likely show a histogram with a peak on the far left, meaning the colors are all fairly dark.
  4. Look for peaks in the middle of the histogram indicating lots of midtones. These might be more muted colors that are showing up in your picture, or grays. If you see a large peak right in the center of your histogram, this means the colors aren’t super bright (like whites and highlights) but they’re also not very dark (like black tones and shadows).
    • Many photos will have several peaks spread out around the middle.
  5. Take a look at any peaks on the right side showing bright areas. If you see a large peak on the right side of the histogram, this means your image has lots of white in it. These could be highlights or any other bright spot of light. Pictures with a high brightness are also called “high key.”
    • The peak on the far right means that most of the pixels are in the bright area.
    • A high key picture might show a bright reflective ocean or a bride wearing a wedding dress on a sunny day outside.
  6. Interpret peaks on the left and right sides as a high-contrast image. Most people want their image to have a high contrast so the colors jump out at you and look vivid against one another. If your histogram is showing big peaks on both the left and right sides, your photo has both lots of brights and darks to create a powerful image.
    • Make sure they’re full peaks, meaning an upside-down ‘U’ shape, and not just half of a peak.
  7. See peaks in the center of the histogram as a low-contrast image. If your photo has low contrast, that means it doesn’t have colors or tones that stand out against each other and isn’t very visually impactful. A low-contrast image will show a histogram with large peaks that are only in the center and none to the left or right sides.
    • This means the histogram is telling you that a high number of the pixels are in the mid-tone range.
  8. View the averaged tones in your photo using a luminance histogram. While most histograms are either green, blue, or red, you might see a histogram for your photo that's white. The white one is the combination of the red, green, and blue histograms together. This shows you the averaged color tones and how the different levels of red, green, and blue brightness are spread out in your picture.
    • Your luminance histogram might be black instead of white, but it represents the same thing.

Creating the Best Picture

  1. Look at the edges of your histogram to see if peaks are cut off. If your photo’s histogram is showing big peaks that are cut off on the left or right side, this means your photo is over or under exposed. Pictures that are over or under exposed aren’t showing all of the details possible and should be edited, if possible.
    • If you see cut-off peaks on the left side, your photo is under exposed, and if you see cut-off peaks on the far right side, your photo is over exposed.
    • If you’re seeing large peaks that are on the left or right side but have a full upside-down ‘U’ shape, that’s okay.
  2. Aim for peaks that are spread out across the histogram. The goal is to have low, high, and mid tones represented in your photo so that it’s well-balanced. If you see peaks in the histogram that are spread out nicely from the left to the right side, this means your photo is properly exposed and has a nice contrast.
    • If your photo doesn’t show a histogram with peaks that are spread out, try adjusting the settings to alter the tones by clicking on the histogram brightness and sliding it to the left or right.
    • Avoid having peaks that are only in the center of your histogram because this means your photo has a low contrast.
  3. Adjust your photo’s exposure so the histogram's peaks are balanced. Use a photo editing software to alter your picture’s exposure. Adjust the peaks so that they’re all visible and spread out, with the most peaks on the left and right sides so you have a high contrast photo. As you adjust the exposure settings on your histogram, you’ll notice the colors change slightly.
    • A great balanced picture will show a histogram with high peaks on each end and lower peaks in the middle.
    • Each different photo editing software will be a little different, but most of them let you drag the color and brightness settings to the left or right using a sliding bar.

Tips

  • Look at the histograms for several different photos and compare them to help you understand them better.
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