Histogram of photo

The histogram can be displayed on the screen of most digital cameras while previewing photos. In fact, even among veterans who have been involved in photography for many years, many people still do not understand the role of the histogram. Most photography enthusiasts' camera screens are set up so that the entire screen is used to display photos. In fact, in professional photography creation, histogram plays a vital role. The histogram can not only indicate whether there is overexposure or underexposure, but also show the distribution range of different light and dark. Checking the histogram when previewing a photo will allow you to judge exposure more accurately than simply viewing the photo.

This article briefly introduces the meaning of histogram expression.

Simply put, a histogram is a two-dimensional coordinate axis that expresses what the camera can accommodate from the darkest to the brightest. The length of the horizontal axis represents the total range of the camera from left to right, from darkest to brightest. The far left represents all black and the far right represents all white. The vertical axis length represents the number of pixels. We all know that a photo is composed of tens of millions of pixels, depending on the camera model and settings. The vertical axis represents the number of pixels gathered at this brightness. The higher the graphics in a certain part, it means there are more pixels of this brightness in the photo. To put it bluntly, this is the continuous histogram, or waveform graph, that we generate when we collect enough statistical data. Essentially, it is a statistical chart of the brightness of pixels in a photo.

Understand the meaning of the histogram. We'll start by thinking about what an ideal histogram would look like. From a purely theoretical estimation, most people would think of it. The theoretically ideal histogram should look like the figure below, a continuous gentle mountain shape.

At this point, many photography experts or teaching materials will immediately start to correct it and say, no, this is not an ideal histogram. Let me say that, yes, if all other considerations are discarded, this is a theoretically ideal histogram shape, if there is such a picture. Now that we know what a histogram means, we can imagine what it would look like if we had such a photo. This should be a photo with pixels ranging from 0, the darkest, to 255, the lightest, on a gray scale. And this photo has the largest amount of pixels in the mid-tones. There is high contrast from the darkest to the brightest, and there are bright mid-tones that take up most of the picture. This is a perfectly exposed photo. In theory, of course.

In actual shooting, whether it is due to the limitations of the shooting environment or the need for creative intention, we will never take such a photo.

If you take pictures of clear and beautiful skies, vast seas, and the horizon where sea and sky meet. The mountain shape must be shifted to the right because the bright color is the dominant color.

If you are photographing dark night lights, gloomy alleys, or even brightly colored flowers, it is not wrong if the histogram shifts to the left.

Even most of the time in the photos we take, the histogram is not a mountain shape with a high center and low sides (such as the title picture of this article). But as long as your objective environment and subjective creative intention are to express this contrast between light and dark, there is no right or wrong shape in the histogram shape.

Of course, if the number of pixels increases sharply on the left or right side of the histogram, and then forms a high cliff at the edge, it means that there is a lot of underexposure in your photo (the night sky in the picture above) There is a large area of ??underexposure) or overexposure. So photography is an art like painting and music. The fact that we cannot see the image of the characters in "Nude Descending the Stairs" does not affect it as a great work. It depends on what the author wants to express in the work.

The histogram cannot tell you whether the exposure is right or wrong. Photography is art, not mathematics. The histogram will only tell you the pixel information in the photo. It is up to the author to judge whether this information is exactly what you want to express.