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June 21, 2014

Histograms Explained: How a Simple Tool Can Help You Nail Exposure Every Time

HistogramCameras these days come with a veritable plethora of tools to help you expose your images properly, everything from built-in exposure meters to zebras and false color displays. However, there's one tool that is often overlooked, despite the fact that it's available on nearly every digital camera today. The histogram. It's an extremely simple tool, but when used properly, it can help you make sure that you never blow out your highlights again.

In this short excerpt from John Greengo's CreativeLive course, The Photography Starter Kit, he talks about what the histogram is, how it works, and how you can use it to nail your exposures.

In short, the histogram is a chart, with the horizontal axis displaying all of the greyscale values in your image (with pure black on the left, and pure white on the right), and the vertical axis displaying the density of pixels for each of those greyscale values. Overexposure and underexposure can be judged simply by seeing whether or not the mass of pixels on the histogram touches either side of the display. In Greengo's example below, you can see an example of a properly exposed image, an overexposed image, and an underexposed image, all with the corresponding histograms.

The consensus with histograms is that the majority of your pixels should be in the middle of the scale, much like the first example above. However, depending on how you intend to expose your image from a stylistic perspective, your histogram might look a bit differently. Here are a few examples from RED's fantastic exposing with histograms post (which is definitely worth a read). First is an example of a bright "high key" image that is properly exposed, and the second example is a darker, moodier image that is also properly exposed. Both have the corresponding histograms.

high key histogram

low key histogram

There are a few drawbacks to using the histogram to judge exposure, however. Since it only gives you an overview of exposure by showing you the density of pixels, it can't give you any specific information about which parts of your image are either under or overexposed. Tools like zebras, false color displays, and waveform monitors can give you very specific greyscale information about individual parts of your image, which in many cases, might be more useful.

With that said, for shooters who are on the run and need a quick visual overview of their exposure, the histogram is an absolutely fantastic tool that can prevent you from under or overexposing.

What are some of your favorite exposure tools? Do you regularly use histograms when you shoot? Let us know down in the comments!

Link: Exposure With Red Cameras: In-Camera Histogram Tools

[via PetaPixel]

Your Comment

32 Comments

Always good to touch basis on the basics.

June 21, 2014

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Travis

We rely on Magiclantern to show us the histogram while filming. A valuable tool when we are filming asian weddings as it can get quite hectic at times.

June 21, 2014

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Define hectic.

August 18, 2014

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Asian dude

May I suggest that you make an article about exposing the right, using the histogram. Especially useful when shooting with the Blackmagic cinema camera in raw (connected to a laptop of course).

June 21, 2014

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Robert

Actually you don't need to connect to a laptop. You just turn on the zebra at 100%, or 95% to play safe, and open the aperture just before the zebra is visible.

June 21, 2014

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Robert

June 22, 2014

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james

This is not the same as the exposing to the right technique. Exposing to the right is actually opening the aperture until you get close to overexposing the shot. So the bump, or hill, whatever you want to call it, will be more to the right on the histogram. Since you don't overexpose, using the histogram to make sure of it, you get the maximum range your sensor can capture. You also get the maximum from your shadow and you reduce the noise. It's a very cool technique but you have to shoot raw. :-)

June 22, 2014

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Robert

Reread the pdf

He is correct. This shows exactly the technique you describe.

June 22, 2014

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Gene Wolfe

tx, very clear and helpful technical explanation of histograms

June 26, 2014

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bill

What about the electronic, rather than optical, view finders? Don't you get pretty much what you see there?

June 22, 2014

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DLD

only if you rely on a histogram

even expensive red bomb evfs are no good to judge exposure....hence the use of histograms and hand held light meters,

June 22, 2014

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james

well, light meters are for not just the exposure per se but for a required look ... in other words, a DP says, "I want a 2.8 key-to-fill ratio here" and the only way you can get it exactly as requested is with a meter ... but when you run&gun it on the move, how much time do you have to flick the menu back to histogram, zebras and so forth? ... I see pro videos overexposed all the time, so one would think that you can look at zebras, adjust your exposure, ISO, shutter speed/angle accordingly and just eyeball the rest off a monitor ... at some point, you'll have to know the dynamic range of your camera ... obviously, when you're on a set, you can be more deliberate ...

June 22, 2014

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DLD

If you run&gun it, you would use zebra and your experience with the camera and viewfinder, but if you have time to set up, you would probably use calibrated monitor and waveform. Histogram is useful to me only as additional tool (to determine clipping for example, although zebra at 100 or 105% is sufficient).

July 27, 2014

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Srdjan

But what about ettr when filming in raw. Highlights hold a lot of info and have a better noise ratio

June 22, 2014

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What I understand is even if you're ettr, a pure white is lost information. you'll never recover anything from there.

What ettr does, is telling you how far you can go before losing information in the highlights

June 22, 2014

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I'm talking about Magic Lantern's raw histogram. Very nice tool

June 22, 2014

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Yep very good tools, still you have to use it wisely, for exemple if you shot a scene where there is no white in trying to make it even in your histogram you end up overexposing things. Also when you have very contrasted scene histogram becomes useless as you touch to bottom on both side, for this case so it's good to have the 70% zebra too.

June 22, 2014

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avds

You're right. Histograms are not a perfect tool. No tool is perfect. You always need to be careful. It's hard to be over cautious with equipment. No one should think histograms, or any other tool, put you in an autopilot mode.

June 22, 2014

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Gene

Any news on Blackmagic Camera Update which should have Histograms on the lcd screen ?

It is for this summer....or the next... :)

June 22, 2014

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Manji06

Can anyone explain to me the benefits of a histogram over waveform?

June 22, 2014

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Talking about basics, all exposure metering is done with a neutral grey as a reference. If your subject matches grey, your exposure will be spot on. If your subject is lighter or darker, you have to interprete the metering results accordingly to get a correct exposure.

A histogram, a light meter and waveform monitor all work fine. It is the interpretation of the metering that counts.

June 22, 2014

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June 24, 2014

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June 24, 2014

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Exposure depends on a variety of factors. When shooting in RAW format on a Canon, I generally use the ETTR (expose to the right) method. The on-camera histogram shows what the photo would look like as a JPEG, and can actually be pushed about about a stop past where the highlights appear to be clipping. This will preserve shadow detail in high contrast situations. (The downfall is a slight color shift, so in a high contrast situation, the photographer must decide which is more important.)

When using a Nikon or Pentax that utilizes a Sony sensor (which is capable of about 14 stops of dynamic range at ISO 100 when shooting RAW) I tend to expose using the "correct exposure" technique as described above, as these sensors capture a lot of detail in the shadows that can be restored after the fact.

June 24, 2014

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Hi from Sekonic Meters. Spot metering the scene brightness with knowledge of the capabilities of your camera (know your dynamic range) is the only way to get the very best results from expose to the right. We have done a lot of work on this for still photographers here: http://www.sekonic.com/classroom/webinars/archivedwebinars.aspx My friend Ryan Walters has metering for motion capture nailed. See it here: http://www.ryanewalters.com/SP/sekonicprofiles.html Sekonic has an automated program to find out the dynamic range of your camera called DTS. Check it out. We also developed a technique to nail expose to the right with one reading. I actually do to to measure the scene brightness first. Some years ago, I sponsored a match the histogram to the picture contest. The prize was a Sekonic L-758DR and Exposure Profile target. The winners were mostly medical techs who knew how to read a histogram. Names were included in the contest sign up. I was amazed at all of the recognizable names in photography who flunked the test. Looking at a histogram made from a JPEG is not the best way to get the job done. Looking at your uncalibrated computer screen or monitor is not the best way to do the job. Using a spot meter calibrated to your camera (DTS) is. It is so simple. Why take all the time to make bad guesses that require hours to fix?

July 2, 2014

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Is it safe to say histogram is fancy word for light meter?

July 14, 2014

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Alvin

The histogram on a camera is rather a simple reference of the tonal range of your composition.

July 14, 2014

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Hi, I'm Thomas the DP of Lightman Films. Histograms on cameras are a simple reference of the tonal range of your composition i would say rather than a light meter. Histograms can be good for wedding video photographers for example and for most run and gun situations generally. However a professional handheld light meter used by DP's gives you a more precise control over the exposure enabling you to measure lighting ratios in your scene and provides you the ability for artistic decisions. It enables you to play with light and get creative and gives a pretty accurate exposure i would say. A vector scope does also a great job but it is mostly destined to match the color profile of multiple cameras that shoot all together at the same time. A waveform monitor is the most "appropriate" in my opinion and most accurate way of controlling your exposure for professional work and helps you to watch closely the luminance levels of the whole scene. (Luminance=Brightness)
But this doesn't necessarily mean that its always the case. It all comes down to what you expose for. Are you exposing for shadows, or highlights? If you are exposing a high key shot going for a "washed out look" you can over expose a bit and blow out your highlights. However if you are serious in what you do i recommend as rule of thumb to expose always correct and over-expose in post to achieve the high key effect you are going for if the scene requires so. If you are going for a low key shot, your highlights might not be even close to the 100 IRE threshold of your vector scope however it can also be tricky as you should care not to crush your shadows (blacks) by accidentally going under 0-IRE. And even that isn't 100% correct as you might want to have crushed blacks. So it all comes down eventually the "look" you are going for. Generally i wouldn't say that histogram is a light meter but rather a tonal range indicator. An onboard light meter on the camera is a sensor that measures the ambient light intensity approximately and its usually the less accurate of all. (Using an iPhone app that utilizes the light meter of your iPhone might even worst. ;) A waveform monitor together with and a light meter are the DP's best friend.

"To break the rules, you must first master them."
Jules Louis Audemars and Edward Auguste Piguet

Thomas Alexander
Cinematographer | DoP

July 14, 2014

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1. in a studio (artificial light situation), why not use the screen to simply LOOK at the image and correct the exposure?
2. in bright sunlight, why not simply LOOK thru the viewfinder and correct the exposure?

3. I would love to impress clients by putting a histogram on half on my screen, but honestly I do not remember the situation when after setting the exposure and THEN "checking" the histogram I had to correct the exposure. ( somehow LOOKING at the image is good enough for me )

July 14, 2014

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sceptic

Splendid! Now it's time to explain vectorscope ;)

July 26, 2014

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August 19, 2014

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August 19, 2014

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