Photo Basics

Reading the Histogram

Read the Histogram and Come Home with Great Pictures!!

I have to admit that when my husband who was also learning photography asked me about the histogram I had no idea how to answer.  I had heard of the histogram but never truly understood what it was. So naturally I went searching for the answers.  

What I found was that a good understanding of how the histogram works and reading the histogram will help you achieve the best exposure for a picture.  So…

What Is A Histogram?

In a nutshell a histogram is a visual graph that shows how much of each tonal value (color) from dark to bright that are present in a picture.  You can use it to tell if the picture is properly exposed. A properly exposed image will have tonal values from both shadows and highlights on the histogram. When taking a picture and reading the histogram you also want to make sure that the tonal values captured don’t stack up against either the left or right side of the histogram. 

Why Use The Histogram?

If you rely on the LCD image preview on the back of your DSLR, you might fall into a couple of pitfalls. The preview on the LCD might fool you into thinking you have got the right exposure if it is set too dark or too bright.

Reading the Histogram-LCD Screen

Also in low light conditions, even an underexposed image can seem bright, because of the backlit LCD screen emits light.

In the end, a histogram is more reliable as it doesn’t vary according to the viewing condition.

How To Display The Histogram On Your Camera?

To enable a histogram on a Nikon DSLR, go to the menu and select Playback menu. Then choose Playback display options. Now scroll down to the Overview option and activate it by pressing the right side of the multi-selector button. Then press OK. You can also choose to activate the RGB histogram, which will show you a more complex and detailed histogram.

Choose the playback display options in the playback menu.

Chose the Overview option to activate the histogram display. RBG histogram will give you a more complex histogram.

After you have captured a photo and can see it on the back of your camera’s LCD monitor, just press up or down on the multi-selector button until you come to the overview display.

Canon users can press the info button during image review/playback to bring up the histogram.

How Do You Read The Histogram?

When you look at a histogram the first time, it looks confusing. 

The histogram shows you how many pixels of each tone, from dark to bright, you have in your image. It is just like a light meter, except that it analyzes or reads brightness values in the image you have just taken, and not before you take it as a light meter does.

The horizontal axis (left-right) is about the tone. And the vertical axis (height) shows how many pixels are found at each particular brightness level. You can think of the histogram as a lot of bar graphs all compressed with no space between each bar.

When you are looking at a Histogram you should mostly focus on the horizontal axis. It is far more important what is happening from left to right than how high the graph is.

What Is The Ideal Histogram?

There is really no ideal histogram, as every image and scene is different. However, we can use the histogram to see if the exposure is good or if it has issues, which could be corrected.

Generally, you should try to expose your image, so the histogram doesn’t crawl up the edges of the histogram.

A slight amount of pixels touching the edges is OK, especially if you shoot in RAW since the histogram in your DSLR is based on the jpg-preview version that the camera uses to show you how the image looks like. And as you probably know RAW files contain more data, which makes it likely that you can recover the details, if the histogram touches the edges slightly.

However, if you have spikes up either side of the edges, the exposure will suffer, and it can be difficult to get a decent image out of it.

Histogram Examples-Reading the Histogram

Get your FREE copy of the Histogram Cheat Sheet by clicking here.

Histogram Cheat Sheet

In Summary

A quick look at the histogram will reveal if parts of your image are over- or underexposed.

If it is underexposed, your image will lack details in the highlights. In this case, the histogram will display a heavy concentration at the left side with spikes leaning right at the edge at the left side of the histogram.

How can you fix this? You can do this by opening the aperture a bit (using a lower f-number), using a slower shutter speed, or by increasing the ISO.

If the histogram, on the other hand, tells you that the image is overexposed, you can fix it by doing the opposite. Use a faster shutter speed, close down the aperture (use a higher f-number), or decrease the ISO setting.

It does take time before you will master the histogram. Gradually over time, you will become more skilled in using the histogram.

Make it a habit to look at the histogram, and correct the exposure when you find that it doesn’t match the tones in the scene you try to capture.

That’s it! Of course, you will want to expand your knowledge and learn everything you can to help you take great photos. Check out Finding the Light to learn how light affects your pictures. Enjoy your camera and get out there and practice!

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