Histogram in Photography: What It Is and How to Use It

The importance of the histogram leads us today to update and republish this article, so you don’t lose sight of it 😉 . If you are just starting out in the wonderful world of photography, you will have already realized that photographing is not just pressing a button and try not to cut anyone’s head off. Photography has many variables, many whys, many explanations. While anyone is capable of pressing a button and taking a picture, not everyone is capable of solve it, that is, to visualize it, think about it, and find the best way to carry out or capture your idea. It’s like painting: anyone can draw a portrait, even with a 6 and a 4 (remember? 😉 ), but anyone won’t paint Las Meninas. This requires a lot of technique, a lot of practice, a lot of tenacity and a lot of photographic learning.

If photography is literally “painting with light” you will have already guessed that the secret is to know it, learn it, anticipate it, understand it and get the most out of it.

There are many concepts that you will gradually add to your photographic baggage: Diaphragm, shutter speed, ISO, white balance and a long etcetera. But I dare to say that one of the least resonates in your mind when you start is histogram. Perhaps it is because we find it terribly complicated in a new world full of concepts, but if there is one of those concepts that you have to retain from the beginning, it is this one. And I’ll show you why 😉

What is the histogram in photography?

A histogram is a bar graph used in statistics that shows us the frequency with which certain values ​​are repeated.

In a histogram, two variables are combined, one for each axis. In the case at hand, that of photography, in the vertical axis we find the “number” of pixels. In the horizontal axis, we find the luminosity values. That is, for each of the columns of the graph we obtain information on its luminosity (light or dark) and on the number of pixels that have this quality.

An image and its histogram

What is the histogram used for?

The histogram is the best help that the same camera will give you to know if your exposition it is correct at the same moment in which you take your photograph.

Start to forget about analyzing your images just looking at them through the screen, since this method is Not very reliable; It depends on the ambient light, the quality of the screen, and its own brightness. Don’t wait until you get home to make sure your image was missing a couple of points of light; if you want to start from a well exposed image, foreveralways, you must use histogram to “read” the light of your image.

How do you read a histogram in photography?

We have already said that the horizontal axis shows us the brightness from image. If we focus on the horizontal axis, we can divide it into three zones imaginary. The area located to the left of the histogram informs us about the shades from image. The central area informs us about the areas of medium luminosity, and the right area, about the areas of lights.

There are as many histograms as there are images, so it is difficult to generalize since the histogram is like a fingerprint of each of the images that we obtain. Nevertheless, generallywe can state that:

  • A histogram without information in the shadow area or in the middle area, which brings together all the information in the right area of ​​the image (lights), it is very likely that it is overexposed. It usually reflects not only the information on the right side, but also a number of raised pixels (peaks) in the rightmost area of ​​the image, looking as if they were going to fall off the graph.
Histogram of an overexposed image
  • A histogram that accumulates the information in the area of shades (left), with little or no information in the middle and highlights, is most likely too dark; underexposed. As in the overexposed histograms, the information tends to accumulate in the form of peaks in the left area, seeming that these are going to “come out” of the graph.
Histogram of an underexposed image
  • A histogram with all the information accumulated in a same areatells us about an image with little contrast. Whether the light information is concentrated to the right, to the left, or in the middle zone. You already know that the light contrast is given by the difference between light and shadow in an image, so if the image lacks differentiation between light and shadow, the resulting image is known as a low-contrast image.
  • A histogram with information accumulated at the ends of the graph (in the highlights and in the shadows) and with little or no information in the mid-light area, it is a histogram of high contrastsince the difference between lights and shadows is high, for example a backlit image, would give a histogram similar to the one we proposed.
  • A histogram with several peaks, shows us a scene where certain tones with information other than the predominant value become relevant. For example, let’s put a desert landscape of a general tone homogeneous but in which some Tuaregs dressed in different colors appear in the middle of the landscape. This scenario would probably leave us with a histogram where the peaks would be that light information “different” from the general tone of the image.

Reading examples of a typical case

To illustrate the concept here we bring you 3 examples of 3 similar photographs but with different exposures. Notice how the histogram plot changes and shifts to the right, center, or left depending on whether the photo is overexposed, correctly exposed, or underexposed, respectively.

correct exposure
Histogram of a Correct Exposure
Histogram of an underexposed image
Histogram of an overexposed image

Beware of the exceptions… there are many

I have already commented that the histogram and its reading is like the fingerprint of an image, that is, each image has its histogram “unique”.

It is often said that a correct exposure is the one that shows us a histogram with information in each of its parameters luminous, from the lights to the shadows, and with the values ​​(pixels) well distributed throughout the axis, since in this way the image is considered to have the higher dynamic range; that is, as much tonal information as possible.

  • Now, imagine a snowy landscape in broad daylight. Do you think that an exposure that “straight” in the histogram indicates that we have overexposed too much? In this case, where there are no shadows in the image itself, the histogram cannot reflect shadows, if there are no midtones, it cannot reflect midtones either, so it is likely that the histogram of this image is simply like this; the information is on the right because the scene in front of us is just like that.

Let’s take another example:

  • A histogram reflecting a landscape at sunset. This shows us all the information accumulated in the left area of ​​the histogram, the shadow area. But let’s say there are some interesting white clouds on the horizon. In this histogram, those clouds are not reflected in the highlight area as they should be (because they are bright or light), so it is very likely that your image is lacking in light, that is, that it is underexposed.

As you can see, there is no rule, but as you use it, with practice and logic, you will learn to know how to interpret its results each time.

Image with “good” dynamic range or information in all lights

Where to start to use the histogram in photography

Start by set up your camera to show you the histogram after each shot along with the preview of your image. I would go so far as to say that all digital SLR cameras have this option, and even many compact ones.

Once you have it set up, get used to analyze the image behind each photo. At first, it may be difficult for you to interpret according to the scene, but little by little, you will learn to read the histogram in an agile and effective way and you will get adjusted images with a correct exposure, you will avoid the typical scenes in which the light meter of the camera decides wrongly for you, etc.

the more you know your team and its possibilitiesthe more you decide and less your camera, the better images you will get 😉 .

So… don’t let those mysterious peaks scare you, in a few days you will have mastered the simplest parameters or situations, and in a few more days, you will also master the somewhat more complex situations. In a couple of weeks you will have become the king of correct exposure, aren’t you tempted? 😉 So what are you waiting for? If you put effort into it, in a few days you will be amazed at your own progress and results and you will think… “How could he have lived without knowing the histogram? 😉

And you know, if you found it useful, interesting, and you think someone else might be interested in reading it, don’t hesitate to share it on your favorite social network. And as always, thank you. 🙂