Do you have a digital camera with a histogram function? If you're like me when I first started out in digital photography, then you probably never used it at all.

Not a very smart thing - the camera histogram is a really useful tool which you can use to avoid exposure issues.

This article will show you how you can make better use of that histogram, so read on.
 

Find the Histogram Function

Most of the better digital cameras in the market today have a histogram function. My Panasonic Lumix DMC-FZ20, for example, has a nice histogram that is overlaid on the picture within the LCD. The better cameras allow you to preview the scene with the histogram overlaid, before you click the shutter release.
 

What's a Histogram?

But what exactly is a histogram, you ask? Well, a histogram is a graph that displays how light is distributed in your picture. The left side of the graph represents the shadows, while the highlights are on the right.

In layman terms, that means that if the histogram has a high peak on the left, you can tell that a lot of pixels in the picture are dark, or in shadow. A peak on the right of the graph means that a lot of pixels are bright, or in highlights. Peaks in the middle of the graph represent pixels in the midtones of your exposure.
 

The Histogram of a Good Photo

Right, now let's look at some examples of histograms. Refer to the picture below. On both the left side and the right side of the graph, you can see that there are no high peaks. This kind of histogram tells you that no part of the scene is over or underexposed. In other words, this shot should look good.

The histogram of a good photo
 

The Histogram of an Underexposed Photo

Ok, now let's look at the histogram of an underexposed photo. You can see a spike in the shadows that starts with a peak on the left of the graph. That means that the picture has lost data in the shadows. There's also just a few pixels trailing off the right side of the graph, so a tiny bit of data might have been lost there as well.
 

The histogram of a underexposed photo
 

The Histogram of an Overexposed Photo

You can probably guess how an overexposed photo looks. Here you can see a pronounced spike on the right side of the graph. Do note that the height of the peaks is somewhat low in this picture; that's not an indication of under or overexposure. All you need to worry about is whether they breach the left or right edges of the histogram.
 

The histogram of a overexposed photo
 

Conclusion