- (histogram) A diagram representing the distribution of a variable, in the event that information about its individual values is available. The areas on the diagram are proportional to the number of corresponding observations in each interval, for example annual... ... Economic dictionary
bar chart- (histogram) Frequency distribution graph, which is constructed using rectangles, whose area is proportional to the frequency of finding a given value in the interval on which this rectangle is built. Business. Dictionary. M.: INFRA M,… … Dictionary of business terms
BAR CHART- (from the Greek histos here column and ... gram) (bar chart), one of the types of graphical representation of statistical distributions of any quantity according to a quantitative characteristic. A histogram is a collection of adjacent... ... Big Encyclopedic Dictionary
bar chart- a figure obtained on a plane where Cartesian coordinates are entered and grouped observations are plotted along the abscissa axis, and the number of corresponding observations is plotted along the ordinate axis. The upper part of the geometric contour is a statistical analogue of density... ... Geological encyclopedia
bar chart- in technical analysis, an interval chart, on which each time interval is associated with a straight line segment (stick), the beginning and end of which is the highest and lowest prices period. At the same time, opening and closing prices are marked on... ... Financial Dictionary
bar chart- is a way of graphically representing the distribution of numerical (continuous) data, often used in exploratory data analysis to illustrate the main characteristics of the distribution. The range of possible values of the variable is divided into segments... ... Dictionary of Sociological Statistics
bar chart- one of the ways to graphically represent quantitative data in the form of rectangular “columns” adjacent to each other and corresponding to the frequency of each class of data. Dictionary of a practical psychologist. M.: AST, Harvest. S. Yu. Golovin. 1998.… … Great Psychological Encyclopedia
bar chart- A graph consisting of vertical or horizontal bars whose height or width is proportional to the data values. histogram bar chart [Luginsky Ya. N. et al. English-Russian dictionary of electrical engineering... ... Technical Translator's Guide
BAR CHART- HISTOGRAM, a bar graph whose bars represent frequency (in absolute values or percentage of the total), with which certain quantities(or ranges of values) occur within some data set. see also… … Scientific and technical encyclopedic dictionary
bar chart- noun, number of synonyms: 1 diagram (9) ASIS Dictionary of Synonyms. V.N. Trishin. 2013… Synonym dictionary
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Real-time histograms are one of the most useful features digital cameras, and it is in the majority modern models. The tools are also available in almost any image processing software. However, the histogram is one of the settings that is most often left to the discretion of auto mode, as many (even experienced) photographers simply do not know how to use it. By learning new skills and ever-evolving technologies, we increase our skill and, ultimately, our self-worth. Therefore, it is worth covering the issues of using a histogram. First, let's review what a histogram is.
The on-screen graphic, expressed as peaks and valleys, shows the degree of brightness and its variations that exist in your photo - ranging from black (0%) to white (100%). The histogram is an accurate and clear “guide” to exposure. It reflects the F-band parameters and brightness levels present in the image. You should get into the habit of looking at the histogram every time you take a photo, and it will be much easier to adjust the exposure. Here, for example, is a typical histogram - with pronounced differences in parts. 
The picture shows that in the photo information display window there is a part with histogram data. It can be enabled or disabled in most cameras on the market.
A histogram is a two-dimensional display of the tonal range of a photo, it is indicated on the X-axis. The Y-axis informs about the number of pixels. On the left side are the darker tones, in the center are the medium tones, and on the right are the light tones. In the picture above, most of the pixels are in the middle zone. This means that the photo is uniform, there are practically no overexposures or underexposures (extreme left and right values). These are the optimal settings for most shots, but sometimes you need to work in high or low key.
Using a histogram, you can create any photo, including atypical or perfectly balanced ones. Below you can see several examples in which the difference is clearly visible.
There are three different histograms in the figure. In the first example, none of the details of the image are lost, there are no unnecessary shadows or highlights. The highest values are close to the center of the graph, the curve decreases beautifully towards the edges - like a bell. The graph displays a photo with a large number of bright fragments from the mid-tone range.
The second example is a histogram with a distribution over the entire range. The peak on the right edge shows that there are very bright white details in the image, in which all the details are blurred. The third histogram displays the frame in very dark tones, with virtually no brightest areas. There is very little that is completely black in the image and nothing that is 100% white at all.
Which of the above is correct? This is a trick question. The fact is that the histogram is nothing more than a reflection of the tonal range recorded by the camera sensors. She cannot “tell” whether you took the photo correctly or not. There will be a lot of black parts and bright, white lights in the photo - and there's nothing wrong with that. The same applies to a portrait on a pure white background.
Now let's see how the histogram compares to the real world.
Similarly, histograms can be used to produce high- or low-contrast images (over- and underexposure).
Here are high and low key photos and their histograms
A common technique when shooting subjects where background detail is not needed. This technique is used if it is necessary to emphasize the subject itself. Portraits are often made in a low key, in which you want to highlight the contrast and features of the model. In general, of course, using a histogram will not automatically make you more of a professional than you actually are. However, without any doubt, it will teach you to understand the basics of the image and will become a useful tool with which you can improve your results.
Not all photographers take the time to look at the histogram after every shot, but it's worth doing it at least during post-processing of images. The skill of working with it will expand your capabilities and help you move further on the path of mastery.
- This is a diagram of the tonal distribution of pixels in the image.
From left to right (horizontally) the brightness is indicated, and from bottom to top (vertically) 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 diagram shows how many light or dark shades predominate in the picture, how many green or red or other shades of colors there are more in the picture. Histograms are different. In photography, mainly three types are used:
- General histogram (which is in the figure below).
- 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)
- A hybrid histogram for general and primary colors (often, an RGB histogram is simply superimposed on the histogram).
How to use the histogram
The histogram shows how many dark or light areas there are in the image, and what the overall balance of the image is.
A photo 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 on 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 “highlights” or light tones, so this part shows how many light areas there are in the histogram. The middle - "penumbra" or medium tones. The rightmost part is sometimes called the blown area; if there is a splash in the histogram at the far right, the photo is likely overexposed.
How is a histogram useful?
- It makes it easy to control underexposure (underexposed image) and overexposure (overexposed image). When overexposed, the peak (the top in the chart) will be visible on the right side of the histogram, and when underexposed, the peak will be visible on the left side of the histogram.
- Fine-tune the exposure
- Control color channels in a photo. The histogram can be used to determine the color saturation of an image.
- Control contrast. Using the histogram, you can easily guess how much contrast the picture has.
What should the histogram look like?
There is no single answer to this question. Ideally, the histogram should look like bell shape(when I studied at the institute, this form was called a Gaussian). In theory, this form is the most correct - after all, the image will have few very bright and very dark objects, and the midtones in the photograph will predominate. But as practice shows, everything very much depends on the type and idea of the photograph 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 using such a simple method as a histogram. Therefore, there is no need to reduce the image to a template form using a histogram. The histogram should be used simply as an additional tool when creating a photograph.
Histogram of a photograph. 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 I need to check the exposure of a photo in bright light, when the photo itself is practically invisible on the camera display. This could be the conditions of a summer beach or bright sun in the mountains. Under such conditions, you simply cannot see what is in the picture, so I look at the histogram to roughly estimate the deviations. And secondly, I use the histogram when editing photos, it is very convenient to determine the key in which the photo was taken by the histogram, and sometimes adjust the photo by adjusting part of the histogram curve. For example, sometimes I just take the “highlights” in the histogram and move them to the left with the slider - I move them into the shadows, the photo turns out without overexposure. A histogram like the one shown in this article is provided by ViewNX 2.
conclusions
Histogram - a useful photographer's tool. It’s up to you to decide whether to use a histogram or not; you can do just fine without it, or you can still understand its properties and use it when processing a photograph or correcting an accurate one.
Thank you for your attention. Arkady Shapoval.
How to evaluate the correct exposure and color reproduction of the picture? How do you know if your photo is bright enough or too dark? Of course, all this can be done by eye, just by looking at the photo. However, the eye is an imprecise instrument, and human perception is subjective. Depending on the lighting or background you're viewing the photo against, or even your mood, you may see the photo slightly differently. The display on which you are viewing the photo will also make its own adjustments: not all screens have ideal color reproduction. How to be? How to evaluate an image objectively? An image histogram graph comes to the rescue. I'm sure you've already come across a histogram. But how to work with this graph? Let's figure it out!
The image histogram can be viewed in any more or less serious viewing or image processing program, for example, in the Nikon Capture NX-D converter “native” to Nikon cameras. The same list includes almost all other RAW converters, for example, Adobe Lightroom, Adobe Camera Raw, Phase One Capture One, DXO Optics Pro and others. Of course, the histogram can also be seen in graphic editors such as Adobe Photoshop. The ability to read a histogram will allow you to master computer processing tools such as Levels, Curves and similar ones.
But that's not all! The histogram can be viewed directly in the camera at the time of shooting. This makes the histogram a versatile tool that a photographer always has on hand. Thanks to it, the photographer can evaluate the correctness exposition frame right during shooting.
There are histograms for each of the primary colors of the image (red, green, blue) and their total RGB histogram. There is also a brightness histogram that evaluates the brightness of the frame. It seems to me that it makes more sense to start getting acquainted with it, since it is the easiest to understand.
We look at the histogram on the camera. Modern DSLR cameras usually offer two options for viewing the histogram.
The first way is to view a histogram of already captured images. To do this, just open the captured frame and select the desired mode for displaying it on the camera display.
The second method allows you to see the histogram right at the moment of shooting. In this mode, various shooting information can be displayed on the screen. Including a histogram.
Learning to read a histogram
So what is a histogram? This is a graph of the distribution of pixels with different brightnesses in an image.
The horizontal axis of the graph displays the brightness of the tones in the image. From the darkest (black) to the lightest (white). On this axis there are bars displaying the number of pixels of a given brightness. The higher the bar, the more pixels of this brightness in the photo. For example, in the example of the graphic in the image there are most of the shades of medium brightness - halftones. While there are few dark and light shades.
Because the tones are positioned differently in different frames, each image will have its own unique histogram graph. However, there are still some patterns.
To better understand how a histogram works in practice, let's first learn how to evaluate the brightness and contrast of a photo using it. First, let's look at histograms of frames with technical flaws.
Underexposed (too dark) frame. We see that the histogram graph has moved to the left side of the graph. The histogram seemed to “flow” from the graph field to the left. If the histogram graph falls on the left side, this indicates that there are a lot of dark shades in the photo, while there are absolutely no light shades (the right side of the graph is empty). It can be seen that there are a lot of black spots in the photo, devoid of details, which is why it is noticeable on the histogram graph that there is a lot of black color in the photo. This indicates a loss of detail in dark areas. Instead, we see black spots.
As a rule, a frame with such a histogram is a technical defect, an exposure error. Theoretically, such a frame can be corrected when processed on a computer, especially if the frame was taken in RAW format.
If you see such a histogram on your camera while shooting, it’s time to think about whether you should brighten the frame.
Overexposed (too light) frame.The opposite situation: the histogram “crept” to the right, falling on the right border of the graph. This indicates a loss of detail in the highlight areas of the frame. Instead of details of various shades in the bright areas of the photograph, we see only white spots: what is in the sky, what is on the water. The histogram also shows this.
Typically, pictures with such a histogram are a technical defect. As with the too dark frame, there was an exposure error. However, while it is possible to save dark frames when processing RAW, such overexposed pictures are practically impossible to edit. It is unlikely that you will be able to pull out details from overexposure; the photo will most likely have to be sent to the trash.
Another example of a frame with loss of detail in the highlight areas. In the photo, instead of patches of sky and the girl’s white T-shirt, there are whitish spots. On the graph they correspond to the histogram peak, “stuck” to the right border of the frame. If such overexposure is easy to notice on a computer, then during shooting, judging the frame by eye on the camera screen, you can easily miss it. Nevertheless, this frame cannot be saved and, roughly speaking, is also a technical defect.
It is best to avoid overexposure when shooting. To avoid them, look at the histogram of the image immediately after shooting, use the indication of overexposed zones.
By the way, advanced cameras have a mode for metering exposure based on bright areas. It is designed to protect the frame from loss of information in bright areas.
"Normal" photo. Now that we know what the histograms of shots look like with the loss of detail in the highlights and shadows, let's take a look at an example of a correctly exposed frame. His histogram looks like a hill or a boa constrictor that ate a hat. Such a histogram shows that midtones prevail in the image, and not dark or light areas. At the same time, the edges of the histogram are located close to the borders of the graph, which means that the photo contains pixels of both the darkest shades and the lightest ones.
Such a frame, as a rule, looks quite contrasting and expressive, and it suits perfectly for processing.
Low contrast shot.Its histogram is entirely placed in the chart field, while the edges (right and left) are empty. This suggests that there are neither sufficiently dark areas nor sufficiently light areas in the photo. Nevertheless, such a histogram indicates that the frame is correctly exposed and is quite suitable for further processing, in which you can, among other things, increase the contrast.
It is not always possible to achieve the desired image contrast when photographing. Much depends on lighting conditions, weather, and the selected lens. The main thing is that all the details in the image are preserved, nothing is lost outside the graph.
Multiple peaks in one histogram- this is a completely possible option. Often this happens when shooting contrasting scenes, where there are a lot of both dark and light shades, but there is little room for halftones.
In this case, the left peak fell on dark grass, and the right peak fell on the light sky.
Filming in high key. High key photography refers to shots taken in light tones. Such frames are characterized by a white (light, in any case) background, a general light gamma. Typical scenes are objects on a white background, people against the sky or in backlight. The histograms of such frames may well “creep” to the right. Yes, and some loss of detail in bright areas when shooting such frames is quite acceptable - the photographer consciously sacrifices them to create a general light, airy atmosphere in the picture. When you are photographing a scene in high key, don't be alarmed if the histogram "runs" to the right. In the case of creative photography, I advise you to shoot such scenes with the most correct exposure, keeping all the details in the photo. And the brightness of the image can be increased during processing.
When shooting in low keyon a black background, a completely opposite situation will be observed: the histogram will “run away” to the left. If you want to take a photo against a black background, be prepared for this. For comfortable image processing, I advise you to preserve as much detail as possible. By the way, about how to take such a fiery shot, we have separate lesson.
Gaining experience
Above we looked at the basic, most typical histogram graphs and compared them with photographs. To practice reading histogram graphs, open a folder with your own (or someone else's - it doesn't matter) pictures and study their histograms. Analyze how light and dark shades and halftones are displayed on the histogram, compare them with the photographs themselves. This way you will quickly master this topic.
Bar graph and creativity
The histogram will be an excellent assistant on the way to quality shots. But it is also important to understand that it only gives the photographer background information about the condition of the image. If you're into creative photography, what you want your shot to look like is up to you! Don't be afraid to experiment, but do it consciously. Remember that a technical defect is sometimes distinguished from a masterpiece only by the creative genius of the photographer.
Whether or not you pay attention to what the histogram shows is your personal choice. But every photographer should at least know that such a tool exists and how it can be used. In this article you will learn "read" histogram and recognize the tonality of your photo based on the histogram.
What is a photography histogram?
A histogram is a graph that shows the distribution of tones in a photograph. I draw your attention to the fact that we will talk about the histogram, which contains information about the tones (not colors) in the photo. If we are dealing with an image in RGB format, then in such a histogram all channels will be presented at once.
There are also histograms separately by channels, which show the distribution of the red, green and blue channels (colors) separately in the photo, but I personally don’t use them at all.
Where can I find a histogram of an image?
You can open a photo histogram directly in your camera or during processing in the “Histogram” information window in Lightroom and Photoshop. In Photoshop, the histogram is also presented in the Levels and Curves windows.
In a camera, the histogram is usually called up by pressing the Info button 2-3 times in a row in photo preview mode. This changes the type of preview view - instead of a full-screen photo, additional data about the file parameters and corresponding histograms appear.
How to read a photo's histogram?
A histogram shows how much shadow, midtone, and highlight there is in your photo. The horizontal scale controls the tonality of the pixels, from the deepest shadows on the left, to the midtones in the middle, to the brightest areas of the image on the right.
It is important to understand that the leftmost point is black point(completely blind, underlit areas without details), and the far right point is white point(the most burned out overexposed pixels, information about which is completely lost).
The vertical scale shows the number of pixels of each tonality in the photo. The higher the “peak” of the histogram, the more corresponding tones there are in the image. For example, in the histogram of the photo shown in the examples above, very high peaks occur on the left side of the histogram, which indicates that most of the photo is occupied by dark areas (in this case, the dark background).
How to use a histogram?
Most often, a histogram is used to orientate how correctly is it set? I especially recommend relying on the histogram readings for novice photographers who find it difficult to determine “by eye” whether there is enough light in a photo.
The basic rule in this case is avoid histogram peaks at extreme points, which talk about underexposure or overexposure in the photograph.
Underlight. If the histogram is heavily skewed to the left and there are high peaks at the leftmost point, this means that there are a lot of underexposed areas in the photo, i.e. There is a loss of detail in the shadows.
Peresvet. If the histogram is very skewed to the right, and the high peaks are on the far right, it means that the exposure was set too high, i.e. some parts of the image are overexposed (loss of detail in highlights).
Both situations are two extremes that should be avoided when selecting exposure settings.
Correct exposure. In most cases, a histogram in which the peaks are located in the middle part of the graph indicates that the exposure has been correctly set. But this does not mean that all photos need to be reduced to some standard medium-gray histogram. This does not happen and should not happen.
It is important to understand that each photograph has its own set of lights and shadows, and depending on the subject of the shooting and the artistic idea of the author, light colors or, conversely, shadows may predominate. Accordingly, the histogram of such a photograph will be shifted in one direction. But this does not mean that the exposure was set incorrectly. Let's look at a few examples.
An “ideal” histogram only indicates the predominance of mid-gray tones in the image. This is what the photo above would look like if it were fitted to the “ideal” histogram.
As we can see, the main distribution of histogram peaks is in the middle (midtones). At the same time, the photo looks flat, low-contrast, and clearly lacks saturation in the shadows and highlights. But we got maximum detail in both highlights and shadows. But is this really important from an artistic point of view?
If you initially shoot a plot with a lot of dark tones(dark background, dark clothes, etc.), then the histogram will naturally shift to the left. Wherein gaps in the shadows are allowed, if these failures occur in plot-insignificant areas of the photograph (background, small areas in the shadows on clothing or environmental objects).
The opposite situation is when we shoot very light story(on a white background, against the light, a model with light skin, in light clothes, etc.), then the histogram will be shifted to the right. At the same time d overexposures (completely white pixels) are omitted in the plot important parts photos(background, details in the background, etc.).
Applied to portrait photography plot-important details are, first of all, the skin (face, hands, figure of the model), hair, and to a lesser extent the model’s clothes.
Therefore, the basic rule for checking exposure in portrait photography is no overexposure on the model’s skin. Small overexposures in highlights on clothing and accessories, and even more so against the background, are quite acceptable.
For example, in the photo below, the exposure has been adjusted to capture detail on the subject's face while at the same time producing a clear line of light and shadow across the face. At the same time, the shooting turned out to be almost silhouetted, against the light, against the backdrop of a large window.
Why should you be more afraid of overexposure than failures in the shadows?
IN digital photography(unlike film) the biggest problem is overexposure, because when too much light hits the photo, an area of the photo turns out completely white, which means complete lack of information about the image. Such overexposed areas cannot be restored - even the RAW format cannot save you, because an error was made during shooting and the necessary data for constructing the image was not obtained.
Information in underexposed shadows is still preserved, so details even in the deepest shadows can, in principle, be pulled out in Lightroom (with the inevitable appearance of strong noise). We are not talking about maintaining image quality now.
For clarity, I will give the following example. Photograph of a high-contrast scene with a large variation in illumination between the lightest and darkest areas. Some average exposure value was chosen (neither yours nor ours). As a result, the bright sky outside the window became overexposed (overexposures are marked in red), and the deep shadows inside the room fell into blackness (gaps in the shadows are marked in blue).
When we try to bring back detail in the shadows by lowering the exposure to the limit, we essentially end up with a gray fill in those areas where there were overexposures. It was not possible to return any details (clouds, tree outlines, tonal transitions, etc.).
If we try to restore details in the shadows, then when we increase the exposure to the limit, we can quite clearly see the texture of the wood on the legs of the chairs.
Conclusion
On the one hand, it is much easier to “extract” image details from the shadows, but noise inevitably creeps in; It is impossible to return details from overexposure, but a slightly overexposed (up to +1 exposure stop) photograph can be brought to a decent appearance without the risk of noise.
This is what I personally do (this does not mean that this is the only correct option).
1. When shooting, I avoid overexposure in areas important to the subject.
2. In critical situations, I prefer to slightly overexpose the frame to avoid strong noise when trying to pull out underexposed shadows. Then, during processing, I dim the lights, returning them to “normal”
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