What is a Histogram?

Have you ever saw that little graph on the back of your camera when reviewing a photo – the one that looks like a mountain? That’s called a histogram. Understanding the histogram can help to improve your photography.
The histogram shows you the quantity of all tones in your image. The left side of the graph represents the shadows and the right side represents the highlights.

Reading the Histogram
Checking the histogram is a great way to determine if your exposure is correct or not. You should get into the habit of reviewing it on the LCD screen of your camera after you’ve taken a shot. You should not rely on the photo review solely to confirm if your settings have given you the correct exposure.

The “ideal” histogram will be low on the left-hand side and increase to a peak in the middle, before gradually dropping off again on the right-hand side. There is no perfect histogram and it is normal for them all to look slightly different.

Underexposed or Overexposed?
If the histogram is bunched up on the left-hand side, then your image is probably too dark and therefore underexposed.
If your histogram is bunched up on the right-hand side, then your image is probably too bright and therefore overexposed. When the histogram bunches up on either side like this, it is known as clipping.

Can We Fix It?
Editing software, such as Photoshop or Lightroom can also display a histogram and there may be some scope to correct the exposure here. However, it’s important not to rely on software to correct things that are easily solved at the time of taking the photo.

Let’s look at a few examples. I have opened this image in Adobe Lightroom. You can see the histogram on the top right.  It is bunched towards the left-hand side and you can see that the image is pretty dark. The shadows have no detail in them and would, therefore, print out pure black. This image is underexposed. In this instance, you will want to increase your exposure.

In the image below, you can see the histogram is bunched towards the right-hand side and the image is very bright. Some detail has been lost in the white clouds. This image is overexposed. The highlights are blown out, so you will want to decrease the exposure.

In the last image, you can see the histogram stretches from the left side to the right side and rises to a peak in the middle. There is detail in the shadows areas and the highlights. This histogram indicates a correctly exposed image.

However, like most other photographic rules, once you understand how the histogram works, you can break it to create your own style of imagery. Remember, don’t panic if all your images don’t have an “ideal” histogram. Use it as a guideline to get you in or around the correct exposure. Once you understand how to read it, experiment to create the images you want.

Feel free to leave a comment or ask a question below.