Using histograms: 6 ways to react to common exposure problems

Using histograms: 6 ways to react to exposure problems

Seen a histogram graph on your DSLR or PC screen but not sure how to use one to fix exposure? Read on: it’s easier than you think. In this post we’ll show you how to spot and react to 6 of the most common contrast and exposure problems when using histograms in the field…

Using histograms: 6 ways to react to exposure problems

A histogram is a type of graph. In photography, it is a way of plotting the exposure of a digital image. By looking at the graph, you can see whether a shot is too bright or too dark.

The histogram used by your camera is essentially the same as used by Photoshop – or whichever form of photo editing software you use. The brightness of each pixel in the image is given a value along a 256-step scale – where zero is the darkest, blackest value possible, and 255 is the brightest, whitest value. The 256 steps correspond to all the brightness values possible in a typical JPEG image, which uses an eight-bit scale, where the brightness of each of the three primary colours is given a binary value from 00000000 through to 11111111.

Using histograms is a much more accurate way of judging whether a picture needs a bit more, or less, exposure. It’s not just used for judging exposure: the shape and position of the graph can also tell you about the contrast of the lighting in the scene.

Below we’ve rounded up 6 ways to respond to common exposure problems when using histograms.


Using histograms: under-exposed

01 Under-exposed
The histogram is pushed to the left and fails to register any very bright areas on the graph. Retake the shot, dialling in a positive value of exposure compensation. Try a setting of +1, then check the new histogram.


Using histograms: over-exposed

02 Over-exposed
The histogram is stacking up at the extreme right-hand side, producing clipped highlights and burnt-out clouds. Retake the shot, dialling in a negative value of exposure compensation. Try a setting of -1.


Using histograms: high key

03 High key
Sometimes the picture is meant to bright, with a histogram that peaks on the right of the graph – as in this shot. However, it’s important that highlights aren’t clipped, because they shouldn’t all be pure white.


Using histograms: low key

04 Low key
The graph here stacks up hard on the left, but isn’t under-exposed because the peak on the left corresponds with the black background. Shoot so the image is as bright as possible, without clipped highlights.


Using histograms: high contrast

05 High contrast
Shooting a white building in bright light creates a very-high contrast scene with a histogram that squeezes up at both ends. Detail is going to be lost whatever settings you use. Try a different angle or time of day.


Using histograms: low contrast

06 Low contrast
Some scenes don’t contain strong shadows or strong highlights and create a histogram that sits neatly in the middle. 
To maximise picture detail, shoot so the histogram sits as far to the right as possible.


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