Histograms can be found in almost any modern image editing software. It is my guess that most current digital cameras, including some compacts, can display histograms as well – some even live as you shoot using your LCD screen. Such a persistent inclusion would suggest that histograms are quite important. Even so, many beginner photographers don’t seem to understand what they show. There is nothing wrong or shameful with that, as histograms may appear to be rather complex at first. Truthfully, they aren’t. In this article for beginners, I will try to teach you how to understand histogram. Hopefully, by the end of this tutorial, you will learn to “read” them and see if they are useful to your photographic needs.
1) General Understanding
A histogram is a graphical representation of the tonal values of your image. In other words, it shows the amount of tones of particular brightness found in your photograph ranging from black (0% brightness) to white (100% brightness). As shown in the image above, dark tones are displayed on the left side of the histogram. As you move rightward, tones get lighter. The middle portion of the histogram represents midtones, which are neither dark nor light. Vertical axis of a histogram displays the amount of tones of that particular lightness. Histogram is exposure-dependent, but is also affected by tone curve and other settings.
2) Shadow and Highlight Clipping
If a certain portion of the histogram is “touching” either edge, it will indicate loss of detail, also called clipping. Highlight clipping (areas that are completely white and absent detail) occurs if the graph is touching the right side of histogram. Shadow clipping (areas that are completely black and absent detail) occurs if the graph is touching the left side of histogram. Either case can be often fixed by altering exposure settings. However, you must remember that it all depends on the scene. For example, if there’s sun in your image, it is only natural it will be so bright – completely white, in fact – that highlight clipping will occur.