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12-31-2014, 01:37 PM   #1
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Histogram Help

OK. I read about the histogram and I have a general idea what it is but I haven't a clue how it can help me in my processing nor what it should actually look like. Here is an example on Photoshop of a picture of some flowers. I see the histogram in the upper right part of the program window but I don't know what it means. How can I use it to make my results look better or is it just decoration and of little practical value?


*Edit* The screen capture is from Adobe Bridge, not Photoshop. My mistake, but the question remains the same.

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12-31-2014, 01:46 PM   #2
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The histogram is basically a plot showing how many pixels in your image plot at a certain brightness for the R, G, and B channels (the three colored histograms). The horizontal axis of your histogram goes from darkest left to brightest right. Ideally you get the peak of your histograms towards the middle because 1. That's what the camera is trying to do and 2. That means you have a nice average exposure. It all depends on what you've taken a picture of. If it's a photo of a snowy slope, the peaks should be more to the right, and a photo of a starry sky should have the peak towards the left.

Making adjustments to the sliders from Exposure to Blacks in ACR essentially adjusts the histogram. The easiest way to learn is to just use those sliders and observe what happens to your image and the histogram.

* Generally you want your histogram to be shaped like yours is but covering the full horizontal axis.

* White balance adjustments will shift the peak of the three channels, and in a perfect situation the three color channels would have their peaks essentially line up.

* When you see peaks at the extremes of the histogram, you've over or under-exposed portions of your image. You adjust the sliders as well as you can to fix that.

In reality, you have to go by what looks good because it rarely works out perfectly. It can get more complicated, but I suggest learning by playing around with it, and then check back with more questions.
12-31-2014, 02:00 PM   #3
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I think that will be helpful. It give me a starting place and a general idea of what to look for. Thanks!
12-31-2014, 02:02 PM   #4
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The histogram itself is nothing magic. There is no specific shape that is better or worse, each image is different. But there are certain things that it can be used for.

My process is:
  • First center the curve to adjust the overall exposure. In this image move things to the right maybe a 1/2 stop or a bit more.
  • Next look at the left and right edges, you want to try and maximize the dynamic range. In this image I would increase the whites until the histogram just bumped the right edge.
  • Then look at the left edge and reduce blacks if needed to bump the histogram into the left edge.


That is the really, really quick & dirty version. White balance will make a difference, shadows and highlights can also be adjusted. The most important thing to remember is that this is all to taste, every image is different. Something with a lot of white in it will be loaded to the right. A night scene with a lot of dark areas might be loaded heavily to the left.

12-31-2014, 02:31 PM   #5
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You might find this article helpful:
Using the Histogram to Get Better Photos - Articles and Tips | PentaxForums.com

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12-31-2014, 02:39 PM   #6
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Just these few suggestions have been very helpful. I reprocessed the photo in the above screen shot making the suggested adjustments and now I can see how it works. Thank you very much guys.


Thanks for that link, Adam; I will put that on my reading list!
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