Histograms: Use them to Improve Your Photography

Histograms

Histograms

What is a Histogram

The Histogram is a bar graph that shows what tones are in your photograph. Digital sensors can capture about 5 stops of light.

5 Stops of LightThe histogram shows the number of pixels in the image in each of those zones.

Histogram of an 'ideal' exposure.This histogram is a screen print from Camera RAW. When you shoot in Camera Raw and open your CR2 file in Adobe Camera Raw, you will see a histogram that represents the tones in your photograph.Histogram of an 'ideal' exposure.

From Left to Right, it reads Dark to Bright. The higher the graph, the more pixels in that tone. From end to end, is the 5 stop tonal range. Notice in this image, I have a considerable amount of pixels in each zone. Theoretically, this is good exposure. (As we know, art and photography are subjective.) This histogram shows there’s a good range of tonality in the image. Notice that the far left (very dark) and far right (very bright) areas don’t have any pixels. That means there’s probably good definition in the shadows and highlights.


Histogram illustrating a loss of detail.Notice, in this histogram, the pixels spike at the edges of the histogram – in both the shadows and highlights. This could be a concern as there won’t be any detail in the max black and max white of my image.

Generally speaking, you want to have some pixels in your max black and max white, but you don’t have to have spikes of pixels. The spikes tell us that there is a significant quantity of pixels without detail in the image.

Histogram in Adobe Lightroom Histogram in Adobe Lightroom. This looks like a good exposure for this image. I have a lot of pixel data throughout the 5 zones and I don’t have spikes of pixels at either end. Click to enlarge.

As you can see, the histogram looks very different in each of my examples. There is no “right” histogram and each one will look different. But, the general rule of thumb is to shoot for a bell shaped histogram (similar to my first example). That is, a histogram with the majority of your pixels in the middle three zones with some pixels in the two end zones. That will ensure that you don’t underexpose shadows and overexpose highlights.

Histogram illustrating no details in highlights. In this screen shot of Camera Raw, the histogram shows that there is no pixel data in the highlights.

I mentioned that these histograms are screen shots of Camera Raw. Most DSLR have a setting to display your histogram after every photo. Or, you can view the histogram through your menu later.

You may have noticed that a lot of photographers glance at their LCD after taking a photograph, and just assumed they were previewing their image. Some of them are previewing their image but many are looking at their histogram to decide if they need to adjust their exposure and reshoot.

One thing worth noting, is that the histogram will look a little different on your camera than it will in Camera Raw or Lightroom, the two examples that I’ve used here. The reason is that the examples I’ve used are based on Raw data but the histogram displayed on your camera is based on jpeg data. Jpegs are 8-bit. My Canon 5D Mark II Raw files are 14 bit. So, when I preview the histogram on the camera, it gives me more information that previewing the image on the camera but not as much information as viewing the histogram on my laptop.

Additionally, depending on your DSLR, your camera may display separate histograms for each channel of color (RGB) and/or a black and white histogram.

Reading a Histogram

Now that you know the basics on how to read a histogram, the next step is to practice reading histograms. Start opening your images in Camera Raw, Photoshop, Lightroom, etc to view the histogram. Before you look at the histogram, though, take a good look at the image. Look at your shadows, highlights and the range of tone throughout the image and make a guestimate on how your histogram will look.

Looking at this image, I expect my histogram to be heavy on the left. Looking at this image, I expect my histogram to be heavy on the left.

 

 

Looking at this image, I expect my histogram to be heavy on the right. Looking at this image, I expect my histogram to be heavy on the right.

Notice that the snow scene histogram doesn’t have colors on it because it’s a greyscale image. Here’s an example with many colors:

This image has a lot of color and more bright areas than dark. This image has a lot of color and more bright areas than dark.

How to Use the Histogram to Improve Photography

Expose to the Right

Have you heard the phrase Shoot the right? or Expose to the right? That refers to overexposing your image to get more highlight data on your histogram. Digital sensors are better (more sensitive) at collecting highlight data than shadow data. So, by exposing to the right, you’re capturing significantly more data (more detail). Just be careful not to blow out your highlights (don’t hug the far right side of the histogram).

When You Don’t Want a Bell Curve

If you’re shooting a high key or low key scene, then you don’t want a bell curve on your histogram.

Histogram of a High Key photo

Histogram of a Low Key photo

If you’re shooting high key (bright scene), then most of your information will be in the highlights because you have very little shadow area in your image. In this case, you’ll notice that your histogram is heavy on the right.

If you’re shooting low key, then your image is dark. You’ll have very little highlight area and your histogram will be heavy on the left.

The more you use your histograms, the more they’re start to make sense to you. Using histographs will help you improve your photography and reduce the number of reshoots you need to do.

 

Copyright 2017 Valerie Hayken Up