What is The histogram & how to use it

The histogram explained!

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13

JANUARY, 2019

Photography
Camera settings

If you’re a photographer using a standard DSLR, then chances are you have seen a histogram on your screen while shooting. Some cameras even allow you to see it live while shooting with the LCD screen. Many photographers know the general concept of a histogram, but still, have no idea what it does for you and your photos. This graphic is probably the most misunderstood tool that your camera provides. Rest assured, this article will clear up any confusion that you may have.

 

What is a histogram?

It is a nifty little tool that allows you to see a graphical value of your photo’s exposure. The very left of the histogram shows your darks, the middle shows your mid tones, and the very right shows your whites. The height that each peak reaches represents how many pixels in that unique tone (from 0 for pure white to 255 for pure black).

Histograms are essential because they allow you to see whether or not your photo is too dark, too bright, or “just right.” The term “clipping” refers to photos that are way too dark or way too bright. With the histogram, we can immediately see clipping and correct our exposure.

Take a peek at the example below:

Underexposure:

Let’s take a look at an underexposed example. As we can see, the histogram shows that most activity is to the very left. Since a majority of the activity is to the left, this means that your photo is very dark. You also see a clipping of the histogram on the left meaning a loss of information in the dark areas.

Overexposure:

Contrariwise in this overexposure example, most activity is to the right and indicates a very bright picture. Here you see a clipping of the histogram on the right meaning a loss of information in the bright parts of the photo.

Good Exposure:

Finally, let’s take a look at a “good exposure” on the histogram.  We see that a majority of the activity takes place in the middle. Take a second to look at the right side and the left side of this example. Notice that no clipping appears on either side. This means that your photo isn’t too dark or too bright and indicate no lost information.

Note: That doesn’t always apply in every situation. Indeed, if you are shooting dark subject (or bright ones), the histogram can be shifted more toward one side to represent the tones of the subject (white wall, black car)

When to use a histogram:

The histogram is especially handy to learn how to achieve proper exposure. Using it allows you to view whether or not you need to adjust your camera’s settings. In practice:

  • Clipping indicates missing details, hard to recover, if not impossible, especially in the highlight. What you should try to do is expose to have your graph smoothly touching the side of the left/right edge.
  • A gap in your graph indicates missing information, meaning you can safely shift your exposure.
  • If your histogram does not touch one edge, this means you also can adjust your exposure to have a higher dynamic range.

If you are shooting an extreme contrasted scene, sunset, for example, chances are you won’t be able to keep your histogram within an acceptable range. It doesn’t mean you shouldn’t take the picture. The histogram also has its limitation.

To avoid clipping highlights, most DSLR cameras allow you to turn on the “highlight warning” setting. If your photo is too bright, your screen will blink on the concerned areas. It is really helpful sometimes.

Getting the right exposure is always better in camera but don’t forget that if shooting in JPG it’s even more crucial. Indeed, when shooting RAW, you have more flexibility to recover badly exposed photos in postproduction. If you want to learn about the RAW format here is an article for you: RAW vs JPEG: “What are the advantages of a RAW image?

Recap: the histogram is used to show whether your exposure needs to be adjusted. It is a great tool to use in ALL situations.

Here is something you can practice right now:

Grab your camera and go someplace where it’s well lit. A great place to practice is outside, perhaps at a park where there is much contrast between darks, mid tones, and whites. Switch your camera to LCD view and enable your histogram (for canon users press the “info” button until it appears on your screen).

Now, point your camera at an area where there are shadows. Notice the activity on your histogram. Is the activity moving to the left? If there is clipping on the left, this means that your photo is underexposed and you should either: lower your shutter speed, open your aperture, or raise your ISO until the activity of your histogram is primarily in the middle.

Next, point your camera at an area that is very sunny. Notice the activity on your histogram. Is the activity moving to the right now? If there is clipping on the right, this means your photo is overexposed, and you should either: raise your shutter speed, close your aperture, or lower your ISO until the activity of your graph is primarily in the middle.

Don’t forget, practice is the key!