Understanding The Histogram

One of my favorite tools for ensuring proper exposure and light in my photography is the use of the camera’s histogram. A tool that is often misunderstood and pegged as overly complex or confusing is really just a simple way for your camera to tell you if it got everything in the shot. So what is the histogram? And how can you use it to maximize your efficiency and enjoyment of photography? Let’s take a look.

This is a scene from Glacier National Park shown with the corresponding histogram which indicates it is a dark scene with a good variety of green and blue colors and minimal reds and whites. How do I know that? Keep reading to find out. Photo Credit: Chris Gheen

What is a histogram?
The histogram in your camera or displayed in your photo editing software is really just a graph displaying the amount of varying types of light within your photo. The graph is indicative of a gradient of dark and light tones. Dark tones are displayed on the left, with light tones to the right. The more data points you have on one side or another will tell you if you have a generally bright or dark scene. It is then up to you to interpret this information in conjunction with the scene you are viewing in real life to determine if your shot is properly exposed. By understanding how to read your histogram, you’ll find yourself with better exposures and less work to do in post processing. I also like to use my histogram to help me manually bracket an image, so knowing the intricacies of the histogram can be especially helpful there as well.

How do I read a histogram?
A common misconception is that the histogram will tell you if your image is properly exposed. While that may be true to some extent, the histogram is really only telling you the balance of light within the image. See my last post on metering to gain a better understanding of a tool to help with proper exposure. To have a well balanced histogram (displayed as an even bell curve in the middle of the graph) means that all of the data points in the image are centered on the middle of the light spectrum and should be indicative of a variety of colors within the scene. An all white image will typically be shifted towards the right, while a darker scene will have the majority of the data points centered on the left portion of the histogram. If your data points go off the top of the graph, this just means there is a disproportionate amount of that one type of light. If this is true in your scene, there is no need to make adjustments. However, if you feel that your scene is actually balanced with a wide variety of light and colors, it may be a good idea to revisit your white balance and make sure that your camera is capturing the varying types of light in accordance with your scene.

This scene from Yellowstone has only bright and dark tones, and relatively little color. As a result, you can see the histogram is showing peaks in both dark tones and light tones with little data in between. Photo Credit: Chris Gheen

Some histograms also display colored light points from left to right getting colder to warmer respectively. This means that, when observing your scene outside of the camera, if you see a more green/blue scene like the one above, you can also expect to see your data points skewed to the left. Warmer scenes with more reds and yellows will be skewed to the right. The color balance is based on the assumption that your image is properly exposed as mentioned above, and as such is generally a good guideline for white balance. If you’re finding that your green/blue scene is coming out more purple or even red, you’ll see this on the histogram and know to adjust your white balance to a cooler setting.

When the data points from the histogram are seen going off the sides of the graph, this is called clipping. Clipping occurs when the image is either over exposed or under exposed and will indicate a need to modify your exposure accordingly, either by use of shutter speed, ISO or aperture. The presence of clipping will tell you that your camera is not capturing all of the light points from your scene, and as a result, your image will either have “blown out” lights or darks, depending on which side is clipping. This can be detrimental to your photography because when you insert that image into your post processing program, no matter what you try, you will be unable to brighten or darken the image enough to get that data to display as anything other than black or white (or more commonly a weird pixelated grey). Your camera has captured no data for that portion of the image, and the ability to improve your image is severely limited.

By under exposing the shot, it may not be clipping on the darks, but it looks unnaturally dark and grey, so being conscious of your scene is important when monitoring your histogram.

 

By over exposing the image, you can see an example of clipping the whites, and as such, there is data lost in

Neutrally exposed

Is all clipping bad?
As I’ve mentioned many times before, a lot of things in photography are only good or bad based on your ability to display them intentionally. If your scene has a lot of white in it (like when shooting Yellowstone winter wildlife) you may find that having your histogram tracking to the far right is good, so long as you’re not clipping and losing some of the highlight data. On the flip side, if you’re shooting the Northern Lights with us in Alaska, you’ll almost certainly find that your histogram will consistently be to the far left side of the graph, and you may even be clipping a bit. Depending on your personal artistic style, you may be totally fine with this, as shooting a night sky comes with the understanding that there are simply dark portions of the sky that would appear unnatural otherwise.

Another time that you may find yourself intentionally clipping is when shooting silhouettes or sunbursts. It’s unnatural to be able to look at the sun and make out all of the colors of light coming from it, and as such, your image will likely be blown out in the area right around the sun, especially if other portions of your image are properly exposed. When shooting a silhouetted subject against a brightly light background, again, it is the photographer’s artistic license to expose the image in a way that the silhouetted subject is completely devoid of color, and will thus appear black, both in the image, and on the histogram.

This scene has an intentional silhouette, and as such, it makes sense to intentionally cause the clipping seen on the left side of the histogram. Photo Credit: Chris Gheen

How do I make the most of my histogram?
When using the histogram, the first thing I look for is clipping. This will let me know roughly if my exposure is adequate and (if shooting in RAW) if I’ll be able to make the most of my image by brightening dark areas or darkening the brighter areas. By ensuring I’m not clipping any of my brights or darks, I know that my camera has captured all of the possible data within the frame and, regardless of how the image looks on my camera’s display, I know I’ll be able to manipulate it in post processing to give it the look I want.

The next thing I’ll look for is to see where my light concentration is within the histogram. If I’m shooting a generally bright or warm scene, I’ll want my data points to be more concentrated on the right side of the graph. Darker or cooler scenes, I’ll want to make sure I haven’t over exposed. When shooting landscapes, I often prefer to slightly underexpose, as they create a more moody aesthetic, so I’ll look to the histogram and see if I’ve got some space to play with on either side of my data points, and if so, will typically try to darken my image a bit. When shooting wildlife, I prefer a more documentary feel, so will want to make sure I’m well exposed and my data points are more evenly distributed. This will help to ensure I can provide a clean look that is indicative of the scene as it truly was, rather than being over or under exposed for an artistic quality.

I also like to utilize my histogram to manually bracket my images. By using an automated in camera bracketing, I’ll often find that some of my images are unusable because I’ve clipped too much of my darks or lights, resulting in more work for me when it comes time to blend the bracketed images. By carefully watching my histogram, I can manually bracket my image to ensure I haven’t lost any data, while still preserving the extreme ends of the light spectrum in subsequent frames. I may end up intentionally clipping on one or two frames, but will know that as long as I’ve not caused any clipping on at least one frame, the data is there and I can then be confident that I’ll be able to bring it back in post processing no matter how dark or light the image looks on the viewfinder.

Another great benefit of utilizing the histogram is that when shooting in really dark or really bright conditions (like night photography or under bright sunny skies), I can ensure my exposure is correct without my eyes playing tricks on me. Often times when shooting night scenes, your eyes have adjusted to the darkness, so every shot will appear brighter on the camera’s screen than when you get home and see it on your computer. The opposite happens when you’ve been outside in mid afternoon shooting under sunny skies, and you may think each shot is darker than it actually is. By using your histogram, you have an objective method for ensuring proper exposure that will not be altered by your eyes’ natural adjustments.

By carefully monitoring my histogram, I was able to capture this image at a time that presented itself with little opportunity for fiddling with settings or redoing the shot. Photo Credit: Chris Gheen

Overall, the histogram can be an incredible tool that will help any photographer ensure they got the shot they want. The more you use it, the more you’ll begin to understand the nuances of the light data and be able to maximize your in the field efficiency. Photographers with a good handle on their camera’s histogram will find themselves taking fewer set up shots and having more time to compose compelling images while throwing out fewer images due to blown highlights or shadows. It’s something that I encourage every one of my guests to try when on a trip with Backcountry Journeys and I highly encourage you to try it too. Good luck, and happy shooting!

Chris Gheen

 

 

 

 

 

 

Chris grew up exploring the mountains of North Carolina, originally with his family on weekend camping trips and later as a self taught rock climber and backpacker, leading him ultimately to a degree in Recreation Management from Appalachian State University with a focus in Outdoor Experiential Education. Immediately after graduating, Chris drove west, knowing the mountains and opportunities for adventure were much bigger. Since then, he has worked in a variety of guiding applications, from small leadership non-profits, to adolescent wilderness therapy, to commercial hiking and tourism guiding in California, Arizona, Utah, Colorado, Wyoming and Montana, always with a camera in hand. Chris loves teaching and sharing his passions and experience with others and is sure to provide careful insight and education whenever the opportunity arises. Chris currently resides in Bozeman, Montana where easy access to Yellowstone National Park allows him frequent trips into the park to photograph wildlife and the unique geologic features of the area. When not behind the lens, he spends his time backcountry skiing, ice climbing, and mountain biking, always on the lookout for a new unique perspective to photograph. The mountains have always been a point of inspiration for Chris and he is excited to capture the beauty of the natural world in an effort to share the space he is so privileged to work in with those around him. For a look at some of Chris’ work, visit his website www.chrisgheenphoto.com

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