Histogram is one of the most important and powerful tools for controlling image exposure. And with a few moments of reading, you’ll understand that some simple rules can make you a much more powerful image editor.
Have you ever taken a picture and thought it was great on the LCD of your digital camera, but did you notice that it was overexposed on your computer screen? It can be hard to tell if an image looks good on a small, bright screen, but fortunately, there is a tool you can use to determine whether the image is too light or too dark: the histogram of your camera.
This is a feature that used to be reserved only for more advanced cameras but in recent years has been incorporated into entry-level cameras and even many smartphones.
Here’s how to get the most out of the histogram, which will allow you to get the correct exposure in your images.
What is histogram?
The dictionary definition of a histogram is a graphical representation of the data distribution, usually displayed as a bar chart. In digital photography, this relates to the pixels that make up your image, and a histogram on your camera displays where each pixel is distributed, from pure black to pure white, and in brightness.
In practice, it looks like a chart, with a series of peaks and valleys. The higher the peak, the more bright pixels. This is the tonal distribution of your image and by reading it you can evaluate the exposure of your image on the LCD or EVF of your camera.
The histogram can usually be found in an image as you scroll through your photos (depending on the playback mode of your camera, it may or may not be enabled by default).
Many cameras also allow a live histogram display, either on the rear LCD or in the case of non-mirror cameras – on your viewfinder.
This is incredibly useful because you can check your histogram by shaping your image and adjusting its exposure.
How to use a histogram?
Although one of the best ways to quickly and accurately judge exposure, the histogram is often overlooked by amateur and novice photographers.
After all, if you do not know what it is, a histogram looks just like a weird chart, and many people have no idea how to use it in their favor. In addition, the “ideal” histogram is different for each photo, and changes depending on the appearance you want. So when you are not comfortable with the histogram, there can be a lot of hesitation in trusting it.
Fortunately, at the most basic level, a histogram is not difficult to understand: the horizontal axis shows the tonal distribution (dark to light), while the vertical axis shows the number of pixels in a specific tone and remember, the higher the peak, more pixels in that tone exist.
The extreme left of the horizontal axis shows the darker areas of the image, then moves to medium (mid tones) and lighter on the far right. In a very bright image, for example, you will see the chart data toward the middle and right of the histogram.
You will lose detail where your image is very light or too dark, and you will notice if a photo is overexposed or underexposed in the histogram as missing or far right extreme pixel information. At this point, you should adjust your settings to compensate try a different shutter speed, choose a larger or smaller aperture, increase or decrease ISO, or adjust exposure compensation.
Depending on the situation, sometimes an unequal distribution is acceptable. If you are photographing snow, a white object or something against a white background, the histogram will display more data points on the right.
The opposite is true when you are photographing a dark scene or a black object. The key here is to know what you want your image to look like and to expose it properly to get that result. By itself, the histogram is just a given, not the right or wrong in any situation; you need the context of your desired image to assess whether the data in the histogram will give it to you.
The histogram is not an infallible tool for shooting perfectly exposed photos because this is not always possible. You can not push a button and create a better image – not even the camera’s automatic setup is smart enough to do that. But think of it as a handy tool that quickly tells you what the exposure levels of your photo are, instead of you having to just guess by looking at the image on the LCD. As your picture improves and you learn how to adjust the settings to compensate, you will also learn how to read the histogram better.
You can also use the histogram in applications such as Adobe Photoshop or Lightroom to improve image quality during post-processing. It can help you more accurately match the appearance and exposure of a series of images you may be editing, or even analyze your images after a session to see how you can enhance your photography.
If you need help, have doubts or concerns, do not hesitate to leave a comment in the comment box below and we will try to help you as soon as possible!