How-To Read a Digital Histogram
Your digital camera has a simple but powerful tool that can help you evaluate the exposure of your images. It’s called a histogram, and it’s essentially a representation of the contrast and dynamic range in each image. A histogram shows the content of each exposure typically using a range from 0 (true black) to 255 (true white). You’ll find the ‘true white’ illustrated at the far right of the graph and the ‘true black’ on the far left. A well-exposed image will show points close to both ends. If a histogram is abruptly cropped on one end, this usually indicates that your image is under or over-exposed.
Each histogram image tells a story about the exposure of the image and can help guide you in making adjustments so that future images are properly exposed.