How to Read Your Camera's Histogram

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One of the magical things that digital photography gives us is the ability to review an image instantly on the back of our cameras, or inside of an electronic viewfinder.  

Frequently, one possible mistake that digital photographers make is when reviewing an image on their camera—they evaluate exposure based on the reproduced image. Why might this be a mistake? Well, both your camera’s LCD and EVF likely have adjustable brightness. Also, you might be viewing your images in bright sunlight or in the pitch black of night. Just as viewing a computer screen at work, or a television in your home, ambient light, screen brightness, and other factors affect the image that you view.

You should evaluate your LCD for composition and look to see if your depth of field, sharpness, and motion blur or freezing of action is what you were aiming for. Of course, if you have completely missed on your exposure, you may see that in an extremely bright or dark image.

So, how can we fine-tune our exposure if we cannot trust what our eyes see on the reproduced image? The answer is: the histogram. Luckily for us, the manufacturers of digital cameras have given us the histogram to use as a tool to evaluate exposure on a digital image more precisely.

The Camera’s Histogram(s)



 


 
Luminosity Histogram Color Histograms

Most modern digital cameras have four histograms. The primary one is the luminosity histogram that shows overall brightness of a scene. This histogram usually has a monochromatic display—either white data on a black chart, or vice versa. The other three histograms are the color histograms, representing the red-, green-, and blue-sensitive pixels on the sensor. These histograms are generally displayed in their respective color.

(It may help to have your digital camera with you while you read this article, so that you can figure out how to find your camera’s histogram and interpret it. Digital cameras from different manufacturers have different menus, interfaces, and settings that govern when and where your histogram or histograms will appear. Consult your owner’s manual or an online source to utilize your camera’s histogram display.)

Now that you have located your histogram, how do you read it?

 


This example shows a nice mid-tone image. The dark area at the top appears as the peak on the histogram’s left side, but it does not extend all the way to the left edge of the graph.

How to Read the Histogram

First of all, there is an enormous amount of math behind the histogram. Luckily for the math-challenged photographers like me, you do not need to know any of it. For those of you who like numbers, I will attempt to sprinkle a few into the article, but know that the numbers behind the chart are inconsequential to reading it on your camera. If the numbers were critical to translating the data, the graphs would have numbers labeling them. However, there are probably more than a few websites and tutorials out there that dive into the mathematical abyss of bit depths, dynamic ranges, and some other sources of the math behind the histogram. Personally, I like to stay focused on the practical applications of the histogram. If you want to know more, hit me up in the Comments section at the end of the article, and we can nerd-out a bit! OK, back to the histogram…

This histogram’s horizontal (X) axis shows the luminance of the image from pure black on the left edge of the graph to pure white on the right edge. Growth on the vertical (Y) axis indicates the relative quantity of light for the given luminance. To illustrate the functionality using an extreme example, take a photo with your lens cap on and you will produce a histogram that has one spike, from bottom to top, on the left edge of the histogram. Opposite of this, take a long exposure on a sunny day and you will achieve a spike on the right. An image with a balanced exposure will show a “hump” in the middle region of the chart that tapers off as you move left toward black or right toward white.

This middle region of the histogram is for midtone luminance—the gray area(s) between black and white. You may have heard of “50 Shades of Gray.” Your camera, if it does 8-bit sampling, has 255 shades of gray. If you must visualize numbers, the X-axis of the histogram goes from 0 (black) to 255 (white) as you move from left to right.

To effectively use the histogram, you need to know three things:

  1. How to read the histogram (you are about to learn that).
  2. The scene—A consciousness of the brightness, darkness, and contrast of the scene you are photographing is needed.
  3. Your goal—The “proper” exposure or “perfect” spread of midtones is not the goal of each photographer for each image. Know what you are trying to produce.

Let us expand on these three things a bit.

How to read it: The histogram basically shows you the brightness of an image. If you take an image and see the majority of the body of the graph toward the right, this means you have captured a “high-key” image that may appear overexposed. Opposite, a histogram with the data showing mostly on the left is a “low-key” image that might appear underexposed. If you are making an image of a high-contrast scene (very dark and bright areas), you might see a U-shaped histogram. There are almost infinite combinations of light and dark that will register on the histogram.



Here is a low-key image and its accompanying histogram. You can see how the “weight” of the histogram is on the left side of the graph and it tapers rapidly as you move toward the center. The hump in the middle corresponds with the illuminated areas under the benches. Note that the data barely touches the left edge of the histogram. That would indicate clipping of the shadow detail.

 

The scene: I feel this is important, and something I do not see discussed very much on the topic of exposure and histograms. If you take a night photograph of a building and half of your image is a sky as black as a raven’s wing at midnight, you should expect to see a large spike on the left edge of your histogram. Conversely, if the sun is in your image, get ready for a right-side spike. If you are taking photos of a scene with dark shadows or bright sunlight, you need to expect to see this on the histogram and you should not be surprised when the spikes appear on the right or left edge.

Your goal: For those of you who read my article about “Understanding Aperture”, you are familiar with my thoughts about the term “proper” when it comes to exposure. Many guides will say that a certain histogram shows a proper exposure. “Proper” is subjective and photography is art. Art is subjective. If your artistic vision is a photo that is overexposed or one that is underexposed, and you intentionally cause that effect for your image, then “proper” is what you have achieved.



Here is an example of the U-shaped histogram caused by a high-contrast image. The band of LED lights in the middle of the frame and the bright foreground give the histogram a short peak at the right while the majority of the pixels are dark, and this is reflected by the mass on the left side of the histogram.

So, you take those three elements—knowledge of what the histogram is showing you, knowledge of the scene you are capturing, and knowledge of the final image you wish to produce—and then you look at the histogram and evaluate how and if you want to adjust your exposure for the next image by tweaking your aperture, shutter speed, ISO, or by recomposing the scene to reduce the amount of dark or light area in the image.

Beside personal artistic goals, the biggest reason to adjust the exposure, based on histogram data, is if your histogram tells you that you have experienced the horrible, yucky, and unfortunate phenomenon known as “clipping.”

Clipping

Your camera’s digital sensor is much more limited than the human eye in its ability to gather information from a scene that contains very bright and very dark areas—a scene with a broad “dynamic range.” In photography, dynamic range is defined as the ratio between the maximum and minimum areas of luminance in a given scene. The camera will, unless you are manually controlling exposure, try its hardest to create an image that is exposed for the widest possible range of lights and darks in a scene. Because of the limited dynamic range of the sensor, this solution might leave the image with pitch-black shadows or pure white highlights.

A spike touching the left edge of the histogram means that there is shadow clipping. The dark areas of the image are outside of the camera’s dynamic range to the point that the camera cannot discern any information from those regions. The camera says, “By exposing for the major portion of the image, I have created an area of the photo so dark that I cannot see anything there, so I am going to call it pure black.” Spikes touching the right edge are representative of the camera saying the opposite, “When I expose for the major portion of the image, this one region is so bright that I cannot tell if there is an object in that region, so I will call it pure white.”

Here is a simulated (no, I did not blow the exposure!) high-key image. All of the data in the histogram is off to the right and—oops—lights of highlight clipping too!

Here is the same shot, as it was taken, which shows a low-key exposure. Note the spike on the right, corresponding to the illumination from the light bulbs, that shows up on the histogram and shows clipping. This is a good example of the sneakiness of highlight clipping, as there is virtually no buildup of brighter sections leading to the spike on the right edge of the histogram. We also have some shadow clipping as well. In scenarios like this there is really no way to avoid clipping on one or both edges. You just need to adjust your exposure to get the effect you want. Your own eyes will have the ability to see into the shadows while not getting blinded by the lights.

Clipping represents, unfortunately, the loss of data from that region of the image. Digital cameras are known for their ability to extract detail from dark shadow regions of an image, but once the histogram touches the left edge, that data is all but lost to a black abyss, and no amount of post-processing will pull detail from those shadows. Areas of pure white will also be just that—pure white—on your screen or on a print.

Shadow clipping is usually pretty noticeable on the histogram, since there is usually a buildup of data on the left side of the scale that reaches the left edge. Highlight clipping can be a bit more subtle, especially when taking night photographs, as only a small number of pixels in the image might be blown-out highlights. Keep an eye out for the narrow spike on the right edge of the histogram. Many of today’s digital cameras will have a flashing highlight indicator, or “blinkies” function that causes the blown-out light and/or dark regions of a previewed photo to blink so that the photographer can see, without the histogram, that areas are lost to black or white. A good practice is to use both the blinkies and histogram so that you can evaluate what regions of the photos have been clipped and whether you want to make adjustments to the exposure to prevent the occurrence in the next shot. Of course, you can always leave well enough alone and move to your next great image and accept the shadows or highlights. Sometimes, depending on the scene and your camera’s dynamic range, there will not be a practical remedy to the clipping; however, if you can adjust your exposure to avoid clipping, by all means, do so.

Remember that RGB histogram that I mentioned? Well, basically, it shows distribution and clipping in the red, green, or blue channels. Pay attention to the RGB histograms because you might see color clipping in one or more channels while the luminance histogram shows no clipping. This “hidden” clipping might be a big deal for your image, depending on your photographic vision for the picture.

Another thing to mention: the histogram and blinkies are usually based on a JPEG rendition of your image. If you are shooting a RAW file, your actual image will have a slightly greater dynamic range and, the clipping, if there is some, should be reduced.

In summary, the histogram is a remarkable tool to have in your tool box and one of many gifts that digital photography has bestowed on photographers of all skill levels. When reviewing your images, be sure to base your exposure adjustments moving forward on the histogram data, look for clipping and blinkies, and do not judge an exposure based on the preview image.

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Nicely explained

Thank you, Carl. And thanks for reading!

thank you i had no glue what the histogram was prior to reading your article. It is a good start for me

Thank you, Joe!

Use this with the Canon

Hi Raymond. Affirmative. Thanks for reading!

Thanks for reading, Jim!

Very  constructive . I learned alot,great info. Thanks for helping out.Jim Bianco

Thank you and thanks for reading, Jim!

You explain what adjustments should be considered if the luminosity historgram shows clipping, but what camera adjustments should be considered if the color historgram shows clipping?

Hi G. Monroe,

You are correct. It was a semi-intentional omission for a few reasons. Color clipping can be caused by how the sensor "sees" color as well as the presence of extremely vibrant colors in a scene and it cannot always be avoided at capture. The interaction of the color histograms can get a little murky [ironic word choice].

Let us imagine a photograph of a bright red tulip on a sunny day. You take the shot an analyze the color histogram and see that there is clipping on the red channel. The areas where the red is clipped are are areas of the image where the red value has reached 255 (if using an 8-bit image), but there may sill be texture information available in that region as long as the luminance histogram (or other 2 colors) are not clipped.

Some photographers will manage color clipping by changing their white balance, but that may introduce unwanted color casts into your image and making a red tulip less red just to avoid clipping might not be the look you are trying to achieve. You can adjust your exposure in the same fashion you would for luminance histogram clipping, but keep an eye on all of your histograms to make sure that, in your quest to avoid color clipping in one or more channels, you do not introduce clipping into other histograms.

I hope that answers your question. It is also important to know that clipping (of any channel) is not always avoidable, nor is it always an unfortunate incident. If vibrant colors, pitch black shadows, or bright lights are a part of your photographic vision then you should embrace them and use them. Knowledge of how the histogram works should help you consciously understand and achieve or avoid clipping to get the photo you envision.

Thanks for reading and thanks for your question!

I am a new boy on your block. Although at 86 ----not in years.

Thank you for your comprehensive camera info.

I am a Nikon man,from Nikomat to D800.1V3.

8 in all. Including  an old Russian/Nikon model.

I will find time to seek advice in your Histogram trainer,I've rarely used this facility in the past.

I enjoyed my recent holiday in New York.Hearing a concentration of U.S.voices took me back to 1943 when I worked on 

American Airbases in U.K. aged 14yrs.    Thanks again, Walter.

P.S. I had to visit Grand Central Stn. But that's another story.

Hi Walter!

Thanks for reading and thanks for supporting our Airmen back in the day!

Glad you enjoyed the article!

Thanks, Todd, for this refresher and bringing color clipping to my attention.  Since I shoot in RAW, what is the general percentage of reduction in clipping?  5%?  Is it evenly distributed?  Does it affect RGB differentially?  

Hi Pam! You are welcome!

Your question is harder to answer than you think. My suggestion would be to put your camera in RAW+JPEG mode and then compare the histograms of both the RAW and JPEG image in a post-processing program like Lightroom, Aperture, or Photoshop. The reduction is going to be dependent on how your camera generates the two types of files and possibly, the dynamic range of the image(s).

I would also imagine you would see a difference in the RGB histograms as well. Your best bet is always to shoot raw files to ensure the maximum dynamic range and post processing flexibility. [Between you and I, it took me years to start shooting raw images...but don't tell anyone!]

Great article. I probably don't use the histogram enough but I do use it especially when doing test shots like in a pre wedding get a feel for the lighting. My problem is when I try to shoot bright reds or yellows in a very dark or very light setting. Generally flowers or sometimes wedding cakes. I have much better luck if it's overcast or a neutral light setting. It seems like I can change the color saturation like you mentioned by using white balance, aperture, or shutter speed but that can give any number of shades . Even using a grey card seems to give too neutral and bland colors. I shoot JPEG and don't have the feel for using Photoshop for it's potential. I guess what I'm saying is I try to get as close to what I want in camera but there are times I feel I can take the shot multiple ways and still have a hard time getting what I feel is an accurate or close rendition of what I'm trying to capture.

Hi Doug. Thanks!

I feel your pain. Cameras all see colors and tones differently and sometimes you feel like you need to compromise in one area to add to another inside an image. The human eye is a pretty remarkable piece of hardware and cameras are catching up, but it will take a while before digital sensors have the same dynamic range that our eyes do and the same amazing ability to interpret color information. Trying to get your camera to work as well as your eye can be an exercise in futility! Be careful!

When I photograph something, I try to get it so that the final image looks as close to what I was seeing as I can get...while having it still look like a photograph. I do not chase dynamic range, because I know my camera cannot do it. My $0.02. 

Thanks for reading and commenting!

Thank's for the reply Todd. My take on the subject is sometimes you need to experiment and try going outside the box to get the results you want. My personal goal is to get as close to the results I want in camera too. And you are so right about looking at an image on the back of your camera. You really don't know till it's viewed on your computer moniter. By taking the same shots multiple ways you stand a better chance of getting the result you want or sometimes even coming up with something more artistic looking that you never considered in the first place. Digital photography is so much fun. No film expense and you have instant results in front of you with a record of every setting you used for every picture. I'm strictly an amerture photographer who loves capturing a second in peoples lives and giving back to them a memory. One of the best compliments you can get is "Wow, your camera takes really nice pictures." I just smile and agree. If they really only knew someone with a small point and shoot that understands lighting and what the camera is capable of can outshoot someone with the most expensive gear available shooting on full auto every time. I'm fortunate in that I've been able to get the Canon 5D Mark ll and some nice L glass. This allows me to be able to shoot in low light conditions and get more creative with depth of field and what I do or don't want in the background. It's just a joy I had with my father who got me started with one of those old Brownie cameras you looked down thru the viewfinder on top of the camera. He's been gone for almost to years now but it was so much fun to show him what todays cameras are capable of and some of the things you can do in lightroom with editing. Happy shooting!

Hey great article, although I knew already how to read my histogram it's nice  Mr. Vorencamp spedded it all out for those folks that are not sure about their exposures. Keep up the excellent service you provide everyone!

Mr. Cordeira,

Call me "Todd." [Insert smiley face emoticon.]

Thank you, sincerely, for your compliment. I am glad you enjoyed the article

Thank you Todd. This histogram article is really concise, but also very clear with all of the pertinent information. Thanks for leaving the math out. Very helpful info.

Thanks, Mike. No worries about leaving the math out! I only use math when I absolutely have to use it! Photography, thankfully, is only as math-heavy as you want it to be!

Is it true that the histogram shown on the back of the camera is based on the JPEG representation of the image or is it based on the RAW? I capture images in RAW format only. Many times, I adjust the exposure based on the histogram on the back of the camera. Then when I load it in Lightroom, it looks like it was about a stop underexposed.

Is this becuase the histogram is based on the JPEG processed or is it some setting in Lightroom. I am not importing with any presets.

Thanks
Binu

Hi Binu,

Thanks for your question. In general, the camera is showing you a histogram based on a JPEG version of your RAW file. I have found rumors that the Leica S2 and some Phase/Leaf medium format backs show histograms representing the RAW image, but I cannot confirm this.

For your particular issue, I might set my camera to RAW+JPEG to compare, in Lightroom, the two histograms. If the RAW one is left-shifted then you can trace it back to the camera. If they both look the same in Lightroom, you can scratch your head and wonder why the RAW images, when taken alone, are showing up underexposed. One stop seems like a lot of difference between a JPEG and RAW to me.

Please let me know what you discover. You have me curious! Thanks for reading and good luck unraveling the mystery!

One of the most succinct, well-illustrated, and focused explanations I've seen. And, rarely do I see an article mention the important aspects of the scene and the goal. Despite having read quite a bit on the subject I may have learned something. Since I shoot RAW I've ignored the histograms. Perhaps I shouldn't. It sounds as if you're saying that though clipping on a histogram is based on a JPEG and therefore may show clipping when less or none will occuron the actual RAW file, there may still be some value in looking at the histogram to see if matches what you expect to see based on your goals. Of course no clipping on the JPEG-based histogram, would guarantee none on the RAW, even though the reverse is not true. Am I reading you correctly there? Well-done article!

Thanks, Dale!

I am glad you picked up something from the article. Yes, definitely check out your histograms, especially if you are shooting an area with a large dynamic range or expecting to see some clipping. LCDs are very accurate, and if you feel you are getting what you need, you do not need to incorporate a magnifying glass and 30-minute intensive histogram study for each image you make, but a quick glance might give you enough pause to re-take that shot (if possible) to nail a better exposure than you did on your first attempt.

Regarding your last question, yes, you are reading me correctly. I cannot think of an example of an image where the JPEG showed no clipping, but the RAW file did. I'm sure anything is possible in the electronic brain of the camera, but if that ever happens, it would likely be an indication of some sort of malfunction or of a localized, previously undiscovered photographic metaphysical anomaly.

Thanks for reading!

I am an electrical engineer that had absolutely no idea what a histogram was, and even with better than average analytical abilities, thought a general knowledge of the subject would be too daunting – so I did not pursue it.    Based on reading your other great articles, I was confident this was the time to start my education on the subject.  Your 10-minute article makes me now feel totally comfortable with the subject, leaving me with the desire to take pictures, just to look at the histograms.  Thank you very much!!!

RSR,

Don't forget, the best histograms accompany the best photos!

Thanks for reading!

No offense intended, but especially since we no longer have to pay for film and processing, I find it far easier and faster just to bracket my exposure rather than mess around with a histogram.

Tell that to a sports shooter ...

MARK,

No offense taken! Bracketing is certainly a viable way to help ensure a good exposure!

Thanks for reading!

article reading a histogram

Yep.

Thank you for your effort trying to explain histogram, which is indeed a crucial part of our time cameras. I think I will stick to your advise avoiding numbers for a while until I become totally familiar with histogram.

Thanks, Mohamad! I am glad you enjoyed the article!

Super article! Brought me to an understanding on how to use histogram!
Thanks

No worries, Carlton! Thanks for reading!

Thank you for this very well written article, Todd!  

Ashish,

Thanks for the thanks and thanks for reading!

Nice lesson!

Thanks for reading, Uner!

Thank you

You are welcome, Stephen!

save article

Saved!

Great article. This will make me pay more attention for proper exposures. Thanks!

Thanks for reading, Mark!

Excellent article! The basics are very clearly explained. Thank you.

Thanks, Khalid!

very helpful and easy to understand!

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