Histogram, What It Is and How to Use

Today we will talk about a very important subject: histogram.You will learn what that means and what it has to do with photography. Come on?

What is a histogram?

When you do a medical examination, his name is usually similar to the term we’re using today, isn’t it? CBC, Eeg are some examples of medical examinations. In the photo, histogram is not much different from an exam, despite not being a doctor and having nothing to do with it. But, Yes, histogram is an examination, but the different intensities of light in an image. Is the representation of them in the form of graphics and you’ve probably come across that way in your camera, although you may still be unaware of the fact by not knowing the subject, but not for long!

Histogram display

Most compact cameras cannot display of the histogram. But, you can see it in virtually every manual cameras. To give you an idea what we’re talking about, you can look at the pictures that we have and also imagine a mountain full of peaks, surrounded by a rectangle. Looks like it makes no sense, it’s just a drawing for many, but for professional photographers, viewing a histogram shows very valuable information.

Here you can see the histogram read by three different post production programs and I chose this picture that made a show of singer Soledad here in Rio, because the lighting of the entire show was predominantly red and blue and so is easier to identify the channels.

In the first image the preview was made by ACDSEE PRO 7 and are enabled the red channels (red), blue (blue) and luminosity (brightness), actually what I usually use more.

In this image the preview by Adobe Camera Raw and you can see clearly that the reading is the same in all three programs. In the Adobe Photoshop CS6, you have the possibility to view more clearly, what I like best, you can see the 4 separate channels, or in the first dialog box, put to “colors” and show all together.

\And as I read it?

Horizontally, we can see 256 shades of brightness when reading a histogram. The reading is 0 to 255 and must be done from left to right. The number 0 means black, and will gray tending to and clearing more and more, and the 255 is white. The darker shades are between 0 and 127 and the lighter of the 128 255.

Analyzing the histogram vertically, are 100 levels to consider. The reading is done from bottom to top and from 0 to 100. The larger the area of the image with a particular tone (black, grey or white), the greater your level in the vertical scale, closer to 100.

Facilitating with examples

Therefore, taking an all-white image, that means she is at 255 in horizontal scale and can only be at 100 on the vertical scale, because the white occupies the entire image. In the histogram, the representation would be a single vertical line at the top and on the right.

But, if the image was completely black, it would be the other way around. The luminosity is zero and, as it occupies the whole image, in vertical line stays at 100. Graphing, we will have a line to the top too, but this time if standing on the left.

And with the intermediate tones? If you occupy the whole picture, the line goes to the top also, representing 100% of the vertical scale. Your place in the horizontal scale will depend on the shade of gray if it is lighter or darker. If it’s darker, it will be more for the left side and lighter, to the right side.

Do you understand? Just got easier with the examples given? It’s hard for you to do a picture completely white, gray or black, but we need to give these examples to understand how to work the histogram scales.

See this picture I did in two different situations, by day, no flash and then at night, also without flash, you realize that even with the candles lit, there is much more information of shadows in the image on the left than on the right. And even if it wasn’t visible, the histogram is not there let us fool.

Analyzing pictures with a histogram

Having as a common photo model, we can make a histogram analysis as follows: imagine a person posing in front of a white background, a wall, for example. We call this high key chart, i.e. the histogram graph will be much more to the right than to the left. Now, analyze a photo of someone outdoors at night. As the background is dark and there are poor lighting, you may already know the answer: the histogram shall hang to the left. This graph is called the low key. Easy, isn’t it?

It is possible to make corrections in the histogram and, of course, in the photo, using image editors that have the option to adjust the levels.

Silhouettes and contrast images

The silhouettes as they appear in the histograms? In this kind of photos, the background is unclear, but people are with dark contours.The answer is: the chart peaks, in this case, focus on the external ends, due to the contrast between the very different tones.

In the graphs with high contrast colours, with many light tones or dark, reading is U-shaped, a central curve.

Images with little contrast represent total absence of shades too light or too dark and the graph is with a predominance in the middle in gray tones.

As this nice cat that someday somewhere crossed in front of me, and to my pleasant surprise, I discovered that one of my zillions of pictures, it was the perfect example. Thanks kitten!

Digital cameras

Here at A2zcamerablog.com, most digital cameras are better for photos low key than high key, because they prevent the image has enough brightness to produce a pure white tone, even in dark photos.

And how have you noticed it’s easier to balance the images of day.

I photographed many years events and have many photos that same post produced has more information of shadows, which is already 99% natural nocturnal events, in the same way that all Photo Studio that I did, there’s much more information because they are light in light controlled environment like this under there!

And because I need to know how to read the histogram?

The histogram is a guarantee of you show how much has your photo, it’s not a reality for many photographers or hobbyists, have calibrated monitors.

If you print a photo and it comes out too dark or too light compared to what you see on your monitor, using the histogram you will discover whether the picture really is a problem, or if it’s the monitor that is. I use this a lot in my workshops because depending on the angle at which I see the picture of my student and often these cameras are in the Sun, just the histogram ensures that photometry really is correct.

That is, he guides showing the equation of lights in your photo.

Oh, so cannot be neither to the right nor to the left, has to be in the Middle? I always use 3 parameters, photometry, the histogram and the most valuable asset, your common sense. In this picture the Studio up there, could risk saying that is nearly blown off, but actually she’s with the light I wanted.

If I use all the time? Whenever I’m in doubt, even though the photometry is correct, if I happen to find the photo “strange”, I turn the display of the histogram. And on two occasions he saved me. The first when I switched places for my impressions, and “boy of printing” insisted that it was my picture was dark and not the auto-correction of the equipment he was using that breaking down everything. And another, in a print event in time, the technician responsible for the impression insisted that my photos were blown up, after checking the histogram, and reinstalling the driver, everything was perfect!

Remembering that each equipment will have a different way to trigger the display of this histogram, look in your manual, and just a tip, in the Nikon cameras, is penis isespecially complicated to configure, but once done, just use.

Questions, comments, suggestions and why not praise  put here in the comments!

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November 12, 2017

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