If you are starting in the wonderful world of photography you will have already realized that photographing is not just pressing a button and trying not to cut anyone's head. Photography has many variables, many whys, many explanations. While anyone is able to press a button and take a picture, not everyone is able to solve it , that is, to visualize it, think it, and find the best way to realize or capture your idea. It's like painting: Anyone can draw a portrait, even with a 6 and a 4 (Do you remember? ;-)), but not everyone will paint the Meninas. This requires a lot of technique, a lot of practice, a lot of determination, and a lot of 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 background: Diaphragm, shutter speed, ISO , white balance and much more. But I dare to say that one of the least resounding 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 are any of those concepts that you have to retain from the beginning, it is this. And I will show you why
WHAT IS THE HISTOGRAM?
A histogram is a bar graph used in statistics that shows 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, on the vertical axis we find the "quantity" of pixels . On the horizontal axis, we find the brightness values . That is, for each of the columns of the graph we obtain information about its luminosity (light or dark) and about the amount of pixels that have this quality.WHAT IS IT FOR?
The histogram is the best help that the camera will give you to know if your exposure is correct at the same moment you take your picture. Start forgetting to analyze your images only by observing them through the screen, since this method is unreliable ; It depends on the ambient light, the quality of the screen, and its own luminosity. Don't wait to get home to make sure that your image lacked a couple of points of light; If you want to start from a well exposed image, always , always, you must use the histogram to “read” the light of your image.HOW DO YOU READ A HISTOGRAM?
We have already said that the horizontal axis shows us the brightness of the image. If we focus on the horizontal axis, we can divide it into three imaginary zones . The area to the left of the histogram informs us about the shadows of the image. The central zone, informs us about the areas of medium luminosity, and the right zone, about the areas of lights. There are as many histograms as images, so it is difficult to generalize since the histogram is like a fingerprint of each of the images we obtain. However, in general , we can affirm that:- A histogram without information in the shadow zone or in the middle zone, which brings together all the information in the right area of ??the image ( lights ), is very likely to be overexposed . It usually reflects not only the information on the right side, but also a high number of pixels (peaks) in the most right area of ??the image, it seems that these were going to leave the graph.
- A histogram that accumulates information in the shadow zone (left), with little or no information in the middle zone and the light zone, is very likely to be too dark; underexposed . As in the overexposed histograms, information tends to accumulate in the form of peaks in the left area, it seems that these were to "get out" of the graph.
- A histogram with all the information accumulated in the same area , tells us about an image with little contrast . Whether the light information is concentrated on the right, on the left, or in the middle zone. You already know that the light contrast is given by the difference between lights and shadows in an image, so if it lacks differentiation between lights and shadows, the resulting image is known as a low contrast image.
- A histogram with the information accumulated at the ends of the graph (in the lights and in the shadows) and with little or no information in the middle light zone, is a high contrast histogram , since the difference between lights and shadows is elevated, for example a backlit image , would give a histogram similar to the one we propose.
- A histogram with several peaks shows a scene where certain tones with information other than the predominant value become relevant. For example, let's put a desert landscape of a homogeneous generalized tone but in which there are tuaregs dressed in different colors in the middle of the landscape. This scenario would probably leave us with a histogram where the peaks would be that “different” light information from the general tone of the image.
EXAMPLES OF READING A TYPICAL HISTOGRAM
To illustrate the concept here we bring you 3 examples of 3 similar photographs but with different exhibitions. Notice how the histogram drawing changes and is placed to the right, center or left depending on whether the photo is overexposed, correctly exposed or underexposed respectively.BEWARE 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 "unique" histogram . It is often said that a correct exposure is the one that shows us a histogram with information on each of its light parameters , from the lights to the shadows, and with the values ??(pixels) well distributed throughout the axis, since it is considered that the image has the greatest dynamic range ; that is, as much tonal information as possible.- Now, imagine a snowy landscape in broad daylight. Do you think that an exhibition that "right" in the histogram indicates that we have overexposed too much? In this case, where there is 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 so; the information is on the right because the scene in front of us is just like that.
- A histogram that reflects a landscape at sunset. This shows us all the information accumulated in the left area of ??the histogram, that of shadows. But let's say there are some interesting white clouds on the horizon. In this histogram, those clouds are not reflected in the area of ??lights as they would correspond (since they are bright or clear), so it is very likely that your image lacks light, that is, it is underexposed.
WHERE TO START
Start by configuring your camera to show you the histogram after each shot along with the preview of your image. I would say that all digital SLR cameras have this option, and even many compact. Once you have it set, get used to analyzing the image after each photo. At the beginning you may find it difficult to interpret according to which scene, but little by little, you will learn to read the histogram in an agile and effective way and you will get adjusted images and with a correct exposure, you will avoid the typical scenes in which the camera's photometer decides for you wrongly, etc. The more you know your equipment and its possibilities , the more you decide and the less your camera, the better images you will get . So ... That those mysterious peaks do not scare you, in a few days you will have mastered the simplest parameters or situations, and in a few more days, you will also dominate the somewhat more complex situations. In a couple of weeks you will have become the king of the right exposure, don't you tempt yourself? What are you waiting for? If you put effort, in a few days you will hallucinate with your own advances and results and think… “How could he have lived without knowing the histogram? And you know, if you found it useful, interesting, and you think that someone else may be interested in reading it, do not hesitate to share it on your favorite social network: Facebook, Twitter or Google+. And as always, thanks.