Photography Histogram Explained

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Today’s DSLR photo tip, the photo histogram explained, involves using the (gulp) histogram. This is another of those features found on most of the higher end cameras that you probably aren’t using. But you should!

What is the histogram?

The photo histogram is that graph that looks like a mountain range with spikes shooting up at seemingly random places. The scary thing is that when you see it, it looks really technical. Most of us immediately try for the land speed record in turning it off.

photo histogram

“Correct Histogram” captured by Bruce

It really isn’t that hard or confusing. Plus, it can go a long way to getting better exposure on our images.

All the histogram does is graphically display the tonal ranges in your photo from the darkest black areas to the lightest white areas. The left side is for black, the right side is for white.

Why should we use the histogram?

Why not just look at our LCD and make adjustments from there? Glad you asked…

I’ve written other articles (discussing picture controls) where I’ve said that the LCD is not accurate. What you are seeing on the LCD screen is not necessarily what is going to show up on your computer. It is really easy to do a whole series of photos and get home only to discover that your masterpiece is under- or overexposed and not at all what you were expecting.

Sometimes exposure can be fixed (after hours and hours in Photoshop); sometimes it can’t. If the shadow or highlight details weren’t captured, they just aren’t there to be “fixed”.

Rule of thumb: Use your LCD to check for composition. Use your histogram to check for exposure.

The initial step to understanding how to use a histogram is to drag out your camera’s manual and figure out how to turn it on in playback mode so that you can see both the histogram and the picture. Reading your manual could easily be the most complex part of the operation. This is another of those times when reading the manual (ten minutes of sheer boredom) can dramatically improve your photography–forever.

Once you’ve learned how to turn on your histogram, take a few shots of something.

  1. For this test run, find a subject that is mostly neutral in tone and not mostly dark or light. Take a correctly exposed, “neutral” shot.
  2. Take your first test shot by underexposing your next photo. Check out the histogram. See how the spikes are more to the left hand side of the screen? That’s the side that shows the dark areas of a photo, and since this one is underexposed, it is darker than normal.
  3. Now take a photo of the same subject, but greatly overexpose it. See how the histogram spikes have shifted to the right side? That is the side dealing with the light areas in your photo.
  4. Now look at your original “correctly exposed” photo. The spikes are likely to be more in the middle area.

Spikes at either end of the spectrum, touching the edges of the histogram, tend to indicate a photo that is over- or underexposed, and you will want to make adjustments–but not always.

Caution: the temptation at this point is to automatically set every photo so that the histogram spikes are in the middle. This would NOT be correct. Each photo has its own right or wrong settings, determined by the subject matter and your artistic vision:

  • If you are making a photo showing a lot of snow, a histogram heavily skewed to the right is correct.
  • A scene of a coal bin would correctly produce a histogram heavily skewed to the left.
  • A sunset silhouette will give you spikes on both the left AND right, with a huge dip in the center.
  • A scene with a lot of neutral tones will give us a bell curve in the center.

Experiment with this for a few minutes, and you will quickly understand how histograms work.

histogram on camera

“Out and About Again” captured by Carl Jones

Then, when you are shooting, you will instantly see where your photos can be improved and make the adjustments to your settings before it’s too late. Remember, in Photoshop you can adjust the lightness and darkness of a photo, but you can’t add detail that was never captured.

Today’s challenge is to take this DSLR photo tip–the photo histogram explained–and practice with using your camera’s histogram. It will make a good weekend project for you, and if you want to start winning photo contests, it is worth the effort to get comfortable with using histograms.

About the Author:
Dan Eitreim writes forĀ ontargetphototraining.com. He has been a professional photographer in Southern California for over 20 years. His philosophy is that learning photography is easy if you know a few tried and true strategies.

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5 Comments

  1. Debbie says:

    I understand the histogram for exposure, however, I get confused with the red,green and blue on the histogram. Do I take those in to account when shooting for correct exposure?

  2. Caio Kallas says:

    Thanks! Really cool, simple and explanatory article!

  3. Chelli says:

    Could you please explain more on what the Histgram tells us?
    Why are the colours always different for different photos?
    What does it mean if one Colour has higher peaks than other colours?

  4. Jennifer says:

    This article has given me at least a partial answer to a problem I am experiencing.
    I am relatively new to photography, but I noticed that even though my LCD shows that my pictures appear properly exposed, when I look at them on my computer (and it is calibrated) they are, more often than not, under exposed. Since I shoot raw, I can correct them in Photoshop, but I would rather get it right straight out of the camera than spend time in making corrections.
    Checking the Histogram will take me a long way towards correcting this problem, but is there a way to correct this in camera, so that what I see, as far as exposure is concern, in the LCD is accurate? or is using the Histogram the only way?

  5. >>Since I shoot raw, I can correct them in Photoshop, but I would rather get it right straight out of the camera than spend time in making corrections.

    Unfortunately, if your goal is optimal exposure for the raw, forget the camera histogram, it’s based on the JPEG and one exposes for that differently than raw (assuming again you’re after optimal data from that mode of capture).
    See:
    http://www.digitalphotopro.com/technique/camera-technique/exposing-for-raw.html

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