bar chart

bar chart - This is a diagram of the tone distribution of pixels in the image.

Bar graph. Article from Radozhiva

Bar graph. Article from Radozhiva

From left to right (horizontal) the brightness is indicated, and from bottom to top (vertical) the amount of area of ​​the photograph of a particular tonality. It is often said that vertical columns simply show the ratio of the number of pixels of a particular tonality. That is, the chart shows how much light or dark shades prevail in the picture, how many green or red or other shades of colors in the picture are more. Histograms are different. In photography, mainly use three types:

  1. Total bar graph exposure (which is in the figure below).
  2. A histogram for each of the three primary colors, such a histogram is often called RGB - red, green, blue - red, green, blue (as in other examples)
  3. Hybrid Bar Chart for General exposure and for primary colors (often, just a histogram across exposure overlay the RGB histogram).

How to use a histogram

bar chart

bar chart

The histogram shows how many dark or bright areas in the image, what is the overall balance exposure snapshot.

A photograph with a huge dark area. The histogram is "shifted" to the left.

A photograph with a huge dark area. The histogram is “shifted” to the left.

The histogram is often divided into 3-4 parts. The part of the histogram from the very left edge is called “shadows” or dark tones, since this area shows how strong the dark areas of the image are. The far right part is “lights” or light tones, so this part shows how many light sections are on the histogram. The middle is “partial shade” or midtones. The far right part is sometimes called the area of ​​illumination, if there is a splash in the histogram in the very right corner, then most likely the photo is overexposed.

There are more light areas in the photo than dark ones. Histogram peak shifted to the right

There are more light areas in the photo than dark ones. Histogram peak shifted to the right

Why is a histogram useful?

  1. It makes it easy to control under-exposure (underexposed image) and overexposure (overexposed). When overexposed, the peak (vertex in the diagram) will be visible on the right side of the histogram, and if underexposed, the peak will be observed on the left side of the histogram.
  2. Fine tune exposure
  3. Control the color channels in the photo. Using the histogram, you can determine the color saturation of the image.
  4. Contrast control. According to the histogram, you can easily guess how much the picture is contrasted.
There are more dark areas in the photo than light ones. Histogram peak shifted to the left

There are more dark areas in the photo than light ones. Histogram peak shifted to the left

What should be the histogram?

There is no single answer to this question. Ideally, the histogram view should resemble bell shape (when I was studying at the institute, this form was called a Gaussian). In theory, this shape is the most correct - after all, the image will have few very bright and very dark objects, and the middle tones in the photo will prevail. But as practice shows, everything very much depends on the type and idea of ​​the photo itself. A histogram is a purely mathematical description of photography (art), and as you know, it is very difficult to describe beautiful things mathematically, especially with the help of such a simple method as a histogram. Therefore, there is no need to bring the image to a template form using the histogram. The histogram should be used simply as an additional tool when creating a photo.

Histogram pictures

Bar graph photos. The tone is shifted to the area of ​​light tones. The contrast is not high.

When do I use a histogram?

Personally, I use the histogram in only two cases - when you need to check the exposure of the image in bright light, when the image itself is practically not visible on the camera display. It can be the conditions of a summer beach or the bright sun in the mountains. Under such conditions, it is simply not visible what is in the picture, therefore, I look at the histogram to approximately estimate the deviations exposure. And secondly, I use the histogram when editing photos, it is very convenient to determine the key in which the photograph was taken by the histogram, and sometimes adjust the photo by adjusting part of the histogram curve. For example, sometimes I just take the “light” in the histogram and use the slider to move them to the left - I move them in the shadow, the photo is obtained without overexposure. Such a histogram, as in the examples in this article, gives ViewNX 2.

Classic Histogram Photo

Classic Histogram Photo

conclusions

Histogram - a useful tool for the photographer. Whether or not to use the histogram is up to you, you can do fine without it, or still figure out its properties and use it when processing photos or adjusting them accurately exposure.

Thank you for attention. Arkady Shapoval.

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Comments: 54, on the topic: Histogram

  • Kirill

    And yes, the most important question - what happens when you move the sliders on the histogram in Photoshop? Not in the sense that the photo becomes darker or lighter - this is understandable, but physically. Well, or mathematically - I don't know what to call it more correctly.

    • Sergei

      Yes, it would be interesting to know.

  • Mitya

    Simple and intelligible about the histogram. Thanks to the author! One of the best resources on photo educational program. :-))

  • Alexander

    A histogram is a useful thing. In addition to overexposure, overexposure helps to correctly distribute light across the frame, identify weaknesses in the frame, and fix them in a timely manner.
    I’ve been doing digital photography recently, before that I was engaged in film at an amateur level in my youth, as now, when I retired, I decided to load my brains to make life more interesting.
    It’s good that there are sites like yours. You can find out a lot of useful and interesting. Thank you!

  • Tatyana

    The best article about the histogram and clearly, thank you.

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English-version of this article https://radojuva.com/en/2012/02/gistogramma/