I once published an article entitled Shoot (to the) Right On The Histogram Of Your DSLR Camera, which helped to explain how to shoot using the histogram to bring out more shadow detail and better color in your photos while preventing digital noise from occurring. But understanding more about how to correctly read your histogram can really help you out at times when you are not sure if you have exposed your photo correctly or not.
So in this short article I am going to teach you to use your historgram more effectively as a part of your photo taking workflow. In fact, there are times when you may be shooting outdoors in daylight that is creating so much glare that you can hardly see what is on the screen of your DSLR after you have taken a shot. So the histogram in those cases, if you learn how to interpret it better, will tell you a lot more about the level of your exposure, even if you can’t see the actual image on the preview screen correctly.
The histogram itself is a bar chart which is broken down into sections showing you what is known as the dynamic range of your photo or, in simpler terms, the parts of the photo which have absolute black, dark shadows, medium dark tones, mid tones, medium light tones, highlights, and absolute whites. The histogram chart does this by placing your absolute blacks on the far left and your absolute whites on the far right and then everything in the middle is a gradually changing range of blacks to whites. The histogram chart also uses the numbers from the RGB color gamut as a reference. 0 being pure black and 255 being pure white. The numbers for the rest of the tones fall in between.
The chart only shows you though what your picture is made up of, and what is actually there, so there is no correct type of histogram in terms of how the chart is supposed to look. You may have read or been told before that a good exposure shows a histogram in the shape of a wave or an upside down letter U. But this is really only how it should look if you want an evenly balanced exposure without much contrast because the shape of the histogram solely depends on the range of the tones of the type of image that you are shooting. If for example you are taking a low key shot in the studio then the bars of the histogram will be weighted in the shadows on the left hand side of the chart since your image is made up of a lot of shadow. And if your histogram is heavily weighted in one area then it is telling you that your photo has a lot of that particular tonal range. So the histogram follows the tonal range of the subject you are shooting and is purely image dependent. That’s why there is no correct or incorrect type of histogram as I mentioned and why the histogram for a high contrast photo can’t appear like a wave. The diagram below offers you some examples of how the shape of the histogram would look with different types of exposures and tonal ranges:
However, there are a few particular instances where you would want a lot of weight at one end of the histogram chart. One example would be if you were shooting against a white background where you are intentionally trying to blow out the exposure for the background area completely. In this instance you will want some bars at the extreme right of the histogram showing up as pure whites in your photo.
Where the histogram will be the most useful though is to tell you if you actually have enough of the tones that you are trying to achieve in a photo. As an example, it can be a great way to check the brighter tones in your photo when you are trying to capture a high key looking image or vice versa for checking the darker tones in a low key image.
So if you never learned about the histogram, what information it is providing you, or even look at it when it appears on your camera screen, then maybe you can start making use of it now as another helpful tool to tell you if your shots are overexposed, underexposed, or looking just right.
If you have questions about understanding more about your histogram then feel free to post them below as always.