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If there is one tool on your camera that gives you the most accurate indication of how your image will look, it’s the histogram.

It may look intimidating and confusing but don’t be put off. In this tip I am going to demystify what it is and how to use it to improve your photography.

What is a histogram?

A histogram is a visual indicator which appears as a series of vertical lines – sort of resembling a line graph. On most cameras it is visible in your image playback and looks something like this:

It is a representation of the range of tones in your image. From left to right, the first third represents the shadows; the second third the mid-tones; and the final third are the highlights. Lines at the most extreme left indicate pure black and lines at the furthest right are pure white.

How do I read it?

The histogram tells you exactly how your image is exposed. If the lines are predominantly bunched towards the left-hand side then this means that a lot of black / dark tones are being registered, which could suggest your image is under-exposed.

Alternatively if the lines are piled up on the right-hand side it might be that the image is too bright and potentially over-exposed. A classic example of this is when you take a photo outdoors and the sky is featureless white; check the histogram and you will see lines bunched up at the far right-hand side.

So how should it look?

There is no correct way for a histogram to look; it depends on your scene, the lighting and your own creative input. But as a rough guide, a “properly” exposed image should capture a full range of tones without losing any detail, i.e. no extreme left or right lines. If your histogram resembles the image above, like a mountain with the peak in the middle, you’re on the right path.

How should I use it?

All too often people will check the rear LCD of their camera and use that to gauge exposure accuracy. Don’t. Or rather do, but do it in tandem with the histogram – this is where the real data is. Once you get into the habit of checking the histogram you can then adjust your settings accordingly to achieve your desired exposure.

Histograms can be tricky to get your head around – you certainly need more than one minute! The best way is to deliberately take some under and over-exposed images and compare. If you have any questions just shout and I may revisit this tip with a second part in the future.

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