Have you ever taken a photograph and on LCD screen on the back of your camera it looked like it was perfectly exposed. But when you see the photo on your computer screen, it looks either too light or too dark? With most modern digital cameras, you can turn on the Histogram to see the exact exposure plotted on a graph. This way instead of relying on the screen on your camera, you can read the Histogram to accurately see if you have a proper exposure.

A Histogram is a graph that shows you what is light and what is dark in your photograph. Your photo is broken up into individual pixels and plotted on the histogram based on tonality. Black is plotted on the far left, and White is plotted on the far right. The darker tones are plotted towards Black on the left, and the lighter tones are plotted towards White on the right.

The goal is to not have the histogram touching either the left or right side of the graph. That means the pixels on the far right of the histogram are pure white. When something is pure white, there is no information left in the pixel besides pure white. If you try to darken that pixel in post processing, It doesn’t know what color to turn and you will just end up with a gray color. The same goes with the far left side of the histogram, but the far left means the pixel is pure black. There is no information in a pure black pixel if you try to lighten it, and it will also turn gray.

You want the histogram to stay towards center of the graph. You will have the most control and flexibility when adjusting the exposure later in Photoshop or Lightroom when the majority of your histogram is in the center of the graph.

To turn on your histogram, man

 A Proper Histogram

As you can see with the histogram for the snowy road, there is almost no data touching the far left, and no data touching the far right and this photo has a proper exposure. The spike on the right side of the Histogram is all the white snow in the scene. It is easily to blow out the snow in a scene to pure white and the histogram can help you achieve bright white snow while retaining detail on the surface. Make sure to read the Winter Photography Tips to learn how to get great shots in the snow.

With this photo of Portland, Oregon at dusk, the Histogram shows that much of the data is plotted on the dark side of the graph. While much of the data is in the shadows, it is not bunched up against the edge of the histogram. This was the effect I was going for, I wanted to photograph the lights of the city while retaining the colors in the sky. This required a underexposed photo.

 Break the Rules

Now that you understand what the Histogram is, and why you do not want the data bunched up against one of the ends, it is now time to break the rules and bunch those pixels up the edges of the Histogram. This photo is of the Lunar Eclipse from October, 2014. Because the night sky was so dark when the eclipse was taking place I had to underexpose much of the photo. I wanted a proper exposure of the red colored moon and I did not care about the darkness beyond. I knew I was not going to attempt to pull any data out of the darkness in Photoshop so I let it go pure black.

Photography is an art. It is easy to get wrapped up in the technical know how and the rules. That is not what photography is about, you have to break the rules and experiment. But the only way to break the rules is to first learn the rules.