Using your histogram to expose to the right
Most DSLRs, compact system cameras and high-end compact cameras can display an exposure histogram for an image.
It is similar to the Levels histogram that can be seen (and adjusted) image editing software packages such as Photoshop CS6 and Elements 11.
This is a graph that shows the brightness distribution of an image with the peaks indicating the number of pixels (or size of the area) within the image that have a particular brightness. The dark pixels are shown on the left while the bright ones are on the right.
A ‘normal’ histogram for an ‘average’ scene will look something like this:
The majority of the pixels are grouped around the centre of the graph indicating that their brightness is towards the middle of the range, but there are a few darker and brighter pixels.
Underexposing the same scene would produce a histogram like this:
The main body of the peak has shifted over towards the left and the trace doesn’t reach the far right of the scale, indicating that there are no white objects in the image at this exposure.
If the scene is overexposed the histogram looks like this:
The peaks all move over towards the right of the graph indicating that many pixels are brighter than a mid tone.
A large peak at the very highest value indicates that there are lots of completely white pixels, suggesting that some areas are burned out, having no detail or tonal gradation.